A lump of algae-coloured flesh on the sand that turns out to be moving.
A sea hare to about 40 cm and a couple of kilogrammes, shaped like a truncated wedge with the rear end cut off flat, the body warty and coloured olive, brown or grey to match the algae it eats. Two rolled rhinophores stand at the front — the “ears” of the name — and a thin internal shell is buried in the flesh at the back. It is a gastropod, not a nudibranch, though it is grouped with them by everyone who dives.
Grazes on algae and on the film over silt, and can be locally abundant in the shallows. Disturbed, it releases a cloud of purple ink from one gland and an opaque white secretion from another; the combination has been shown experimentally to interfere with a predator’s chemical senses rather than simply to hide the animal. Sea hares are simultaneous hermaphrodites and form mating chains of several individuals, one behind the next. Recorded from the intertidal to about 20 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
