226 of the 1316 species in the index carry a hazard note: the mechanism, a severity, and one sentence on what it means in the water. They are gathered here, most severe first. The list is not confined to one kind of diving or one ocean.
Almost everything on this page is only a problem if it is touched, picked up or leant on. A scorpionfish on the bottom does not approach anybody; it is a hazard to the hand that lands on it. The same holds for the urchins, the bristle worms, the cone shells, the sea slugs whose skin is toxic to handle, and every fish here carrying venomous spines. The single measure that prevents most of these injuries is not putting a hand down without looking at what is under it.
A second group is not avoided by that rule, because the animal comes to the diver rather than the other way round. The drifting stingers are the clearest case: a box jellyfish or a Portuguese man o' war trails tentacles several metres behind a body that is difficult to see, and a diver can be stung by an animal they never saw. What works there is covering the skin, and taking notice of the season and the wind rather than of what is visible from the boat.
A third group is avoided by not being in that water on that day. Saltwater crocodiles are the plain example, and the decision belongs to the people who dive the place every week, not to a visitor reading a page. Local advice about where it is sensible to enter the water is the most useful safety information on any trip, and it is worth more than any general rule written here.
Large sharks are on this page because they can injure a person, not because they are likely to. Incidents involving divers are rare and are concentrated at a small number of known places, which are also the places people travel to in order to see them, under supervision. On ordinary recreational dives anywhere in the world they are not a planning consideration.
Severity and mechanism are recorded in a fixed vocabulary rather than written out per animal, so the same wound is described the same way across the site and the index can be filtered on severity. The categories are defined at the foot of this page.
Nothing here is first aid. The entries state the mechanism and stop; treatment is a matter for a doctor or a local hyperbaric unit.
Get the person out of the water and to medical care immediately.
The saliva contains tetrodotoxin, for which there is no antivenom; the bite is small and often painless, and the animal only rings up when it is being handled or cornered.
The venom is a potent neurotoxin and a bite is a medical emergency requiring antivenom, though the snake is placid and bites almost only when handled or trapped.
Venomous, and a bite requires antivenom; the snake investigates divers closely and should be allowed to do so without being grabbed or pushed away.
Carries tetrodotoxin in its saliva. The bite is small and can go unnoticed, and there is no antivenom; treatment is assisted breathing until the toxin clears. Never handle one and never pick up a shell it might be in.
Strongly venomous. Sea snakes are not aggressive and bites are rare, but a bite is a medical emergency and needs antivenom.
A venomous bite from the sea snake most often involved in bites on people, usually in shallow turbid water or when it is caught in a net and handled.
Nematocysts on the trailing tentacles: venom from the larger species can stop the heart within minutes and the smaller species cause a delayed systemic syndrome, so any sting from a cubozoan is a medical emergency.
Nematocysts on tentacles that trail several metres behind an almost invisible bell; a sting over a large area of skin can stop the heart, and the animal is not seen before contact.
A sting from an animal about the size of a fingernail that is barely felt at the time; the serious symptoms begin twenty to forty minutes later and need medical care.
The harpoon is fired on a proboscis that reaches any part of the shell, including the end a hand would hold, and the venom of the fish-eating species has killed people.
A harpoon-like tooth fired from the narrow end of the shell, carrying a venom that has killed people; this is the cone shell that must not be picked up under any circumstances.
A harpoon-like tooth fired from the narrow end of the shell, carrying a venom capable of killing a person; like every cone, it is dangerous only in the hand, and safe in every other circumstance.
A bite from a large shark that lives in shallow, often turbid coastal water where divers and swimmers also are; it is one of the few sharks regularly implicated in incidents with people.
A bite from a very large predator; incidents involving divers are rare and are concentrated at a small number of places where the animals gather, which is also where the diving for them is done.
Thirteen dorsal spines, each with a pair of venom glands, and the animal's defence is to stay still rather than move, so it will not get out of the way of a hand or a knee.
The most potent fish venom known, delivered by dorsal spines when the fish is trodden on or leant on; it does not flee, because not being seen is its whole strategy.
An ambush from a large predator that hunts at the surface and in shallow water; it is a reason not to enter certain water at all rather than something to manage once you are in it.
The flesh and shell carry saxitoxin and tetrodotoxin, which cooking does not destroy and which have killed people who ate the animal, though the crab poses no risk to a diver looking at it.
An injury that should be seen by a doctor.
Thirteen dorsal spines, plus the pelvic and anal spines, carry venom, and the fish holds position rather than moving off, so a sting comes from contact with a stationary animal.
The first dorsal and both pectoral spines are venomous. The juvenile ball holds together under a light, so it is photographed rather than parted.
Venomous dorsal spines along the raised sail, which is the part of the fish a diver is most likely to touch.
Venomous dorsal spines on an animal that is genuinely hard to see against encrusted rock.
The spines carry venom and the small pincer-like pedicellariae between them deliver more of it; it is the urchin most worth keeping a fin clear of.
Venomous spines above the pectoral fins. It lies buried with only the eyes and mouth clear, which is why it is stood on rather than seen.
Venomous dorsal spines on a fish that lies buried in soft sediment and walks rather than swims away from a hand.
Venomous dorsal spines. Small and cryptic rather than dangerous to approach.
Venomous dorsal spines. A stonefish relative that lies half buried on open sand, which is where people meet it by accident.
Venomous dorsal, pelvic and anal spines. The fish does not flee and will hold its position, so the spines meet a hand that comes too close.
Venomous dorsal, pelvic and anal spines. It does not retreat from divers, so the thing to watch is where it has drifted to.
Venomous dorsal spines and a painful sting. It sits still on the pylon a hand is about to hold.
Venomous dorsal, pelvic and anal spines. It sits in weed and does not move off when approached, so the risk is from a hand or knee rather than from the fish.
Venomous spines and a sting out of proportion to the size of the fish. Common in water shallow enough to stand in.
Venomous dorsal spines, on a fish that sits still and lets divers come very close.
Venomous dorsal spines, on a fish whose fringed outline is what makes it easy to put a hand on.
Venomous dorsal spines. It walks rather than swims and does not move away, so the risk is a hand put down beside it.
Venomous dorsal, pelvic and anal spines. At night it moves towards a light, so it can end up closer than it was.
Venomous dorsal spines on a fish that stays put when a diver comes close, so injuries come from a hand or a knee put down on rock rather than from the fish moving.
Venomous dorsal spines on a large fish that holds absolutely still against rock; the injuries come from hands and knees, not from the animal.
Venomous dorsal spines, as throughout the family. The fish stays put when a diver comes close, so injuries come from a hand or a knee put down on sand rather than from the fish moving.
Venomous dorsal spines. It lies part-buried on the sand a diver kneels on.
Venomous dorsal spines, as throughout the family. The fish relies on camouflage and will not move, so the risk is a hand placed on it.
Venomous dorsal, anal and pelvic spines. The animal does not move when approached, which is how a hand or a knee finds it.
The dorsal, pelvic and anal spines carry venom, and the fish holds position under a ledge rather than moving off, so a sting comes from a stationary animal in a confined space.
Long venomous spines that break off in a wound. A puncture is slow to settle and prone to infection.
Venomous dorsal spines on a fish that buries itself and does not move away. Most injuries are from weight put down on sand that looked empty.
Venomous dorsal spines, as in the whole family. The fish does not move away from an approaching diver, so injuries come from a hand or knee put down on sand rather than from the fish.
Venomous dorsal spines, carried on a fish that drifts into things rather than swimming away from them.
Venomous dorsal spines on a fish that lies buried in soft sediment, so the usual injury is from kneeling or putting a hand down on one.
Venomous dorsal spines on a fish that does not move when approached and is very hard to pick out against rubble.
Venomous dorsal spines run the length of the raised sail, the part of a drifting, motionless fish a diver is most likely to touch.
Venomous dorsal spines and a severe sting. It does not move when approached, which is how a hand or a knee finds it.
Serrated venomous spines in the first dorsal fin and in both pectoral fins. The fish feeds close against sand and structure, so contact is normally with a hand or knee placed on the bottom rather than with a fish in open water.
Venomous dorsal spines set in a buried fish that does not move away. Most injuries are from weight put down on sand that appeared to be empty.
Venomous dorsal, pelvic and anal spines. The fish holds its ground when approached, so contact is a question of where a hand or a camera port goes.
Venomous dorsal spines on a motionless, well-camouflaged fish that sits on the sediment surface where a hand or knee may land.
Venomous dorsal spines, as throughout the family. The fish holds position on rubble rather than moving off, so contact comes from a hand or a fin put down on ground that looks bare.
Venomous dorsal spines, on a fish that holds position against the roof of a ledge rather than moving off.
Venomous dorsal spines, on an animal that spends the day buried in silt.
Venomous spines in the first dorsal fin and on each gill cover, on a fish that lies buried in sand and does not move away; almost every injury is from a hand or a knee put down on it.
Venomous dorsal and gill-cover spines on a small fish that buries itself in shallow sand; the usual injury is to a bare foot in knee-deep water rather than to a diver.
Venomous dorsal, pelvic and anal spines on a fish that relies on camouflage and will not move away, so injuries come from a hand placed on it.
A moray bite crushes and tears and infects readily. The open working jaw is respiration, not threat, but a hand near the hole is a different matter.
Long fine teeth and a habit of repositioning rather than withdrawing; a bite crushes and infects readily.
Jaws that close hard enough to cut, on an animal that strikes upward from a burrow at anything passing over it.
Docile until touched or pulled by the tail, when it bites and holds. Almost every recorded bite followed handling.
Bites when a hand goes into its hole. The teeth are backward-pointing, so the wound is a tear rather than a puncture, and it becomes infected easily.
Bites are rare and are almost always preceded by a clear threat display; a shark that arches its back and drops its pectoral fins is telling a diver to give it room.
A large moray bites hard and the wound tears and infects readily; bites happen when a hand goes into a crevice or when the eel is fed by hand.
Blunt crushing teeth rather than fangs, but a bite still breaks skin and infects. It hunts in very shallow water where people wade.
It bites when trodden on or pulled, and the jaws are hard to release. Look before putting a hand or a fin down on a ledge.
A nesting fish defends a cone of water above its nest and will charge and bite; the teeth take out a piece. Swim horizontally away from the nest, not upward.
A large moray bite crushes and tears and infects readily. Nearly every recorded bite involves a hand in a hole or a fish being fed.
Same as the spotted wobbegong: it bites if trodden on, and holds.
The teeth are long and backward-pointing and a bitten limb is hard to free; bites follow standing on the animal or putting a hand or fin in front of its head.
The skin mucus contains a protein that destroys red blood cells. Handling irritates skin and is dangerous near eyes, mouth or an open wound, the fish is poisonous to eat, and a bite carries mucus into the wound.
A serrated venomous barb on the tail, used defensively when the animal is trodden on, cornered or crowded; the wound is a deep puncture as well as a sting.
One or two venomous spines near the tail tip; stings occur when a ray is trapped, stood on or handled, and cause severe pain and a wound that needs cleaning.
A serrated venomous barb on the tail, driven upward and back in defence; almost every injury is from standing on a buried animal in the shallows.
A venomous barb on the tail, used only when the animal is trodden on. Shuffle rather than step on sand.
Venomous barbs at the tail base, used only in defence. It swims away from divers.
A venomous tail barb, used when the animal is trodden on. It buries in water shallow enough to walk in.
One or two long venomous spines at the tail base; stings occur when a buried ray is stood on or when a diver settles on top of one, and cause a deep, severely painful wound.
The flower-like pedicellariae are venomous pincers that seize skin, detach and go on injecting, so contact anywhere on the animal delivers venom and the pain is severe.
A serrated venomous spine on a tail much longer than the disc, so it reaches well forward. Stings happen when a buried ray is stepped on or cornered, and the wound is severely painful and infects readily.
The tail carries venomous spines at its base and can be used defensively if the ray is cornered or handled; free-swimming rays present no risk.
A calcified club fired fast enough to break shell and crack a camera port; it strikes at a finger put near the burrow.
A smashing club, small but fired at the same speed as its larger relative's. It strikes at what comes into the burrow mouth.
A large needlefish travelling at speed can leap and impale; injuries occur at night and are associated with lights shone across the surface, not with normal diving.
Barbed spearing appendages fired upward from the burrow entrance at whatever passes.
Carries tetrodotoxin, for which there is no antidote. It is a hazard only if eaten.
The most common source of ciguatera poisoning in the region, particularly in large individuals; the fish is harmless in the water.
Paired electric organs in the disc discharge on contact and will do so repeatedly; the shock is delivered to whatever touches the animal, including a hand put down on sand it is buried in.
A discharge from paired electric organs, delivered on contact and repeatable. The ray lies buried and is usually found by touching it.
The nematocysts raise burning welts and blisters that can last for weeks, and the animal sits on open sand at knee and hose height.
Nematocysts on tentacles that can trail ten metres behind the float and go on firing after the animal is dead or detached, so a sting can come from a fragment with nothing visible attached.
Brittle barbed spines that break off in the wound. No venom, but the fragments are a nuisance out of proportion to the injury.
All octopus are venomous and this one is a close relative of the blue-ringed. Its venom has not been characterised, which is a reason for caution rather than a reassurance.
Painful. Unlikely to need more than cleaning and time.
The skin releases grammistin, a bitter mucus toxin, when the fish is handled or stressed; it is harmless through a glove but should not be handled bare-handed or eaten.
The body wall holds saponins that are released into the surrounding water when the animal is damaged or badly stressed, and they irritate on contact rather than sting.
Ejects sticky Cuvierian tubules when handled; they adhere to skin and gear and carry an irritant.
The Cuvierian tubules are strongly adhesive and the body wall carries holothurin, both of which irritate skin and, far more painfully, eyes.
Secretes sponge-derived compounds through the skin. Handling one and then touching a mask or a face is the way people find that out.
Some species eject sticky Cuvierian tubules and others release a red fluid containing holothurin, both of which irritate skin and eyes.
Releases purple ink and a separate white secretion when handled; both are irritants, and the white one has been shown to deter predators chemically.
Secretes sponge-derived compounds through the skin, toxic enough to kill fish confined with it.
Colonies of the genus Palythoa can contain palytoxin, which acts through broken skin and through the eyes rather than by stinging, and the concentration varies widely between colonies.
Secretes sponge-derived compounds through the skin. There is no reason to pick one up.
The skin releases a toxin when the fish is stressed or handled; it is a hazard to other animals in confined water rather than to a diver, but the fish should not be picked up.
Sponge-derived compounds are secreted through the skin. They transfer to fingers, and from fingers to a mask seal or an eye.
Secretes sponge-derived compounds through the skin. Handling one and then touching a mask or a face is how people find that out.
Holds sponge-derived compounds in the skin and releases them into the surrounding water when the animal is handled or confined.
Concentrates toxins from the cyanobacteria it grazes; the same compounds cause skin irritation on contact with the mats.
Releases a toxin from the skin under severe stress, mostly documented in confinement; a diver will not trigger it.
Secretes sponge-derived compounds through the skin. Handling one and then touching a face or a mask is how divers find that out.
Carries defensive compounds in the tissue, which is why an animal this soft moves about in daylight.
Releases purple ink and a separate opaline secretion when handled; both are chemical deterrents and can irritate skin and eyes.
Carries defensive compounds in the tissue and in the papillae, which is the reason an animal this soft and this visible moves about in daylight.
The skin releases grammistin, a bitter mucus toxin, when the fish is handled or confined. It is a contact and ingestion toxin rather than an injury from a spine or a bite.
The skin mucus contains a toxin that irritates. It matters only if the fish is handled.
A phyllidiid, with the family's skin secretions. Harmless to look at and worth not handling.
Pores along the dorsal and anal fins release a toxin that repels predators; it irritates skin and eyes, so a fish handled and then a mask cleared is a bad sequence.
Secretes sponge-derived compounds through the skin, and a large animal secretes a lot of them. The residue transfers to gloves and from gloves to everything else.
The skin of several Pleurobranchus species secretes strongly acidic mucus when the animal is handled. Unpleasant rather than dangerous, and avoidable.
Releases a skin toxin under severe stress, as other boxfish do, mostly documented in confinement; a diver will not trigger it.
Sponge-derived compounds are secreted through the skin. They transfer to fingers, and from fingers to a mask seal or an eye.
The body mucus of some nemerteans carries tetrodotoxin and related compounds, which is reason enough not to handle a worm that cannot be identified.
Stinging cells in the tentacles cause irritation on contact with thin skin; the sting is mild.
The tentacles adhere strongly and sting on contact; it is the anemone most likely to catch a bare hand or an arm laid on the sand.
The tentacles carry stinging cells; contact causes irritation on thin skin and is a reason to keep hands and camera ports clear, not a serious hazard.
The trailing arms sting on contact and are far longer than the bell, so the sting arrives from a metre away from the part of the animal you are looking at; painful on bare skin, not dangerous.
The trailing tentacles carry stinging cells and can extend far beyond the visible body, so the sting is usually taken by a diver who thought the animal ended where the light did; painful rather than dangerous for the species met on a blackwater dive.
Males and young females tear tentacles from Portuguese man o' war and carry them in the arms; the nematocysts on those stolen tentacles still fire, so an octopus this size can sting a bare hand.
Stings on contact and raises a welt that lasts for days. It is the commonest sting on a Caribbean reef because it does not look like an animal.
Contact causes an immediate burning sting and a welt that can itch for days; vinegar rather than fresh water is the rinse, and rubbing makes it worse.
Nematocysts across the whole surface of the colony. It looks like a hard coral and stings on the lightest brush, usually the back of a hand.
Brushing it produces a burning welt that can last days. Wrists, the back of the neck and the gap above a glove are where it usually happens.
It stores the stinging cells of the hydroids it eats in its own cerata and can fire them on contact.
Releases stinging cells into the water around it, so the sting can come from swimming above one rather than from contact.
Stings on contact. The white rings on the tentacles are the batteries of stinging cells.
The disc adheres strongly and stings on contact; the effect on a bare hand is a burning welt rather than a serious injury.
Stores the hydroid's stinging cells in the tips of its cerata and can fire them on contact. Small, and no reason to touch one.
Stings on contact, and releases free-floating packets of stinging cells into the water around it - the cause of the itching that swimmers get without touching one.
Stores the hydroid's stinging cells in the tips of its cerata and can fire them on contact. Small, and no reason to touch one.
Stores the hydroid's stinging cells in the tips of its cerata. Very small, and there is no reason to handle one.
Stings on contact and sticks to skin. It grows in water shallow enough to stand in.
A painful sting from long trailing tentacles that are hard to see. Not dangerous to a healthy adult.
Stinging cells taken from siphonophore prey and stored at the tips of the cerata. They discharge on contact with skin, and are concentrated enough that the sting can exceed that of the animal they came from.
A very large number of fine tentacles trailing well below a bell that may be a metre or more across; the sting is painful rather than dangerous, but the animal is far wider than it looks from above.
Nematocysts on the bell as well as the tentacles, so contact anywhere on the animal stings; painful and long-lasting on the skin but not dangerous to a healthy adult.
Dorsal, anal and pelvic spines carry venom and the sting is intensely painful for several hours; the fish is not aggressive and the risk is from contact and handling.
The dorsal, anal and pelvic spines carry venom and a sting is painful for several hours; the fish keeps its distance and the risk is in handling or in blundering into a wedged fish at night.
The short dark secondary spines are fine, barbed and mildly venomous and break off in the skin, while the long banded primaries are blunt and largely harmless.
Venomous dorsal, anal and pelvic spines; painful to a hand, harmless to a diver keeping clear.
The short dark secondary spines are fine, barbed and mildly venomous and break off in the skin, while the long primaries are blunter and largely harmless.
Hollow toxic bristles break off in skin on the lightest contact and cannot be brushed out, and the burning and numbness that follow last hours.
The hinged caudal blade cuts readily and the wound is disproportionately painful; the risk is in handling a netted or trapped fish rather than in swimming alongside one.
A hinged blade at the base of the tail can cut to the bone and carries venom that makes the wound disproportionately painful. It is a hazard to handling, not to swimming past.
Dorsal, anal and pelvic spines carry venom and the sting is painful for several hours; the fish is not aggressive.
A hinged blade on each side of the tail base can open a deep cut and the wound is more painful than its size suggests; it is a hazard to handling and netting, not to swimming past.
Dorsal, anal and pelvic spines carry venom; the sting is painful but not dangerous, and the fish poses no threat unless handled.
The dorsal spines are venomous and the sting is painful. It is a defensive fish, not an aggressive one, and the risk is in handling it.
A sharp spine on the rear edge of the cheek carries venom; the risk is from handling or from putting a hand blind into a crevice, not from the fish itself.
Venomous dorsal and opercular spines. The fish sits wedged into rubble, so contact is normally with a hand placed on a stone rather than with a fish in the open.
Venomous dorsal spines. It does not move when approached, so the risk is putting a hand on one.
Venomous dorsal, anal and pelvic spines. The fish sits wedged into rubble rather than in the open, so contact is normally with a hand placed on a stone.
Venomous dorsal and head spines on a small fish set deep inside branching coral. Contact is normally with a hand steadying against a coral head rather than with a fish in the open.
Dorsal spines are venomous in this family, though the fish is small and the reported stings are mild.
The jaws are lined with fine recurved teeth and the fish strikes at anything fish-sized that passes close; it has no interest in a diver, but a hand placed on the sand beside one is a hand beside a loaded trap.
A moray, with the family's teeth. It stays in its hole and bites only what comes into it.
A territorial or nesting fish will approach and can bite; the teeth are small compared with a titan triggerfish but the fish is faster to commit.
A fish guarding a nest in shallow sand will charge and can bite; the defended area is small and moving a few metres sideways ends the encounter.
Nesting males charge and nip divers between about October and December. Startling rather than damaging.
It will bite bare skin, taking a small circular nip. Startling rather than damaging, and the reason some divers get bitten repeatedly at one site.
Bites when guarding a nest. The territory is a cone above the nest, so swimming upward away from it does not leave it.
Blunt crushing teeth rather than fangs, so a bite grips rather than tears - and it still breaks skin and infects. It is a hand in a hole that causes it.
Bites if the buried head is trodden on or grabbed, which is the realistic risk given how little of the animal shows.
Bites when guarding a nest, which it does from a cone-shaped hollow in the sand and will follow a diver upward to defend.
A nesting fish will defend the water above its nest and can bite; encounters at nests are much less frequent than with the titan triggerfish.
A powerful ambush predator that strikes upward from the sand, so a hand or knee placed on a buried head can be bitten hard.
Unlike other brittle stars it has jaws strong enough to take hold of skin, and while the bite does no real damage it is a genuine one.
A defensive bite from an eel that lives inside rubble, where the head can be at the mouth of a gap that looks empty. The teeth are blunt and crushing rather than cutting.
Strikes upward from the sand at anything passing close, so a buried head is a risk to a hand or knee put down blind.
A moray bite tears and infects readily. This species is small and stays inside rubble, so the risk is confined to a hand put into a hole.
The spines are long, brittle and puncture a glove. They break off in the wound rather than envenoming it.
A hinged blade at the tail base, as on all surgeonfish. It cuts and is used when the fish is handled.
Two fixed blades on each side of the tail are sharp enough to cut deeply; the hazard is in handling a caught fish.
Long brittle spines that break off in the skin. Painful rather than dangerous.
The two fixed blades on each side of the tail point forward and are sharp; the risk is in handling a netted or speared fish, not in the water.
Stout spines with sharp tips that puncture a hand or knee put down on them and can break off under the skin.
A long spine on each side of the carapace and slender claws that pinch through a glove, on a crab that raises the claws and holds its ground.
The spines are long, brittle and puncture a glove. They break off in the wound; they do not envenom it.
A hinged blade at the tail base is sharp; the hazard is in handling a caught fish.
The spines are long, sharp and brittle and break off in the wound, so the injury is a nuisance out of proportion to the size of the animal.
Sharp lateral teeth on the carapace and strong claws on an animal that holds its ground and grips rather than releasing.
The antennae and the carapace carry forward pointing spines that tear skin. The animal reverses into shelter rather than advancing.
The carapace and the antennal bases are covered in forward-pointing spines that tear skin. It reverses into a hole rather than attacking.
A sharp spine on the cheek that can cut a hand reaching into a hole.
The carapace and the chelipeds carry sharp spines that tear skin, and the animal retreats into its crevice rather than coming out at anything.
White bristles that detach into the skin at a touch and carry an irritant; they are difficult to remove and the burning lasts for hours or days.
The muscle tissue carries a toxin found in no other cuttlefish tested. Not a contact hazard, and not a reason to keep further away than usual.
The flesh, skin and organs carry tetrodotoxin, for which there is no antidote. Not a hazard in the water; the fused beak can take a finger's worth of skin if a fish is handled.
Skin and organs carry tetrodotoxin; the fish is harmless in the water and dangerous only if eaten.
Flesh from this species has been repeatedly linked to ciguatera poisoning in the region; the caudal blade is sharp but not venomous.
Strongly toxic if eaten; harmless in the water to a diver who does not handle it.
The skin and organs contain tetrodotoxin, for which there is no antidote; the fish is harmless in the water and dangerous only if eaten.
The flesh, the skin and the viscera carry tetrodotoxin, which the fish acquires from its diet rather than making itself.
Releases ostracitoxin from the skin under severe stress, as other boxfish do, documented mainly in confinement rather than in the sea.
The skin and organs contain tetrodotoxin, for which there is no antidote; the fish is harmless to divers and dangerous only if eaten.
Skin and organs contain tetrodotoxin; the fish poses no risk in the water.
Releases ostracitoxin from the skin under severe stress, documented mainly in confinement. Not a hazard to a diver, and a real one to anything sharing a bucket with it.
Large individuals carry ciguatera in parts of its range. Not a hazard in the water; included because it is the reason the fish is left alone.
A recorded cause of ciguatera poisoning in parts of the region. It is a reason not to eat one, not a reason to avoid one in the water.
Paired electric organs discharge on contact and can be repeated. The risk is putting a hand on one buried in sand.
Delivers a shock strong enough to be startling but not dangerous. The animal is buried, so the risk is putting a hand on one.
The raptorial club is a smashing weapon and the animal strikes at a finger or hand put into its cavity, which at this size means a bruise or a split fingernail rather than an injury needing treatment.
A barbed spearing appendage fired at a hand put into its cavity, which at this size means punctures rather than an injury needing treatment.
Grooved fangs deliver venom defensively when the fish is seized; the bite is a hazard to a predator or to a hand that grabs it, not to a diver.
All octopus have venom and a hard beak. A bite is defensive, comes from handling, and is a small wound that should still be cleaned properly.
Small venomous pedicellariae sit between the spines and can raise a minor sting on bare skin; the spines themselves are short and blunt.
The mechanism vocabulary, as it is defined for the whole site, with the number of entries carrying each. An animal can carry more than one, so these do not add up to 226.
All 1316 species in one index, which filters on severity as well as group, destination and rarity. Terms used in the notes are defined in the glossary.