Marine life  /  Turtles, sea snakes & crocodiles  /  Olive-headed sea snake
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Species entry

Olive-headed sea snake

Hydrophis major

A thick-bodied sea snake of northern Australian soft bottoms, banded when young and plain when adult.

Size
To 160 cm
Depth
1–25 m
Habitat
Northern sand and silt
Active
Day and night
Range
Australia and New Guinea
Rarity
Australia
4 stars of 5, two or three a season
SP-01
olive-headed sea snake · full body · habitat
4:3 · min 2400px

To about 1.6 m, thick-bodied, with a small head that is barely wider than the neck and a paddle-shaped tail flattened side to side. Young animals are banded in cream and dark olive; adults lose most of that and are plain olive-brown. The paddle tail separates any sea snake from any eel at a glance, and the small head on a thick body separates this one from the more slender species.

It occurs on northern Australian soft bottoms and in New Guinea, hunting fish and eels over sand and among rubble, and it has to surface to breathe. It is strongly venomous, as all sea snakes are, and it is also not aggressive: sea snakes approach divers out of curiosity and around a diver’s fins in particular, and almost every recorded bite involves an animal being handled or caught in a net. The fangs are short and a wetsuit stops most attempts. That said, a bite is a medical emergency and needs antivenom, and the effects can be delayed by hours, so anybody bitten goes to hospital whether or not they feel unwell. Let an interested snake investigate and move on rather than pushing it away.

Where to find:

LocationRarity Best monthsDepthHabitat
Australia Australia editorial estimate
4 stars of 5, two or three a season
Year-round
1–25 m
Northern sand and silt

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.

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