Types of sea snakes

Hydrophis belongs to the family Elapidae, the same lineage as cobras, kraits, and mambas. What sets the genus apart is total commitment to the sea. These snakes are superbly adapted to ocean life: the tail is flattened sideways into a paddle that drives them through the water, the nostrils sit high and close with valves to keep the sea out, and the animal can absorb some oxygen directly through its skin. Excess salt is dealt with by a special gland under the tongue, so a Hydrophis can stay at sea without ever needing fresh water.

The genus ranges through the warm coastal waters of the Indian and Pacific Oceans, from the Persian Gulf eastward across South and Southeast Asia to the coasts of Australia. With 30+ species recorded in our database, Hydrophis is a large and varied group, including the Yellow-bellied Sea Snake, the Olive-headed Sea Snake, the Elegant Sea Snake, the Slender-necked Sea Snake, and the Beaked Sea Snake. In the field, the typical look is a banded marine snake with that giveaway paddle-shaped tail. Most species must surface to breathe, so they are often seen at the top of the water.

Ecologically these are ocean predators. They hunt fish and eels through reefs and shallow waters, and many species give live birth at sea, completing their entire life cycle in the water without ever crawling onto land. That marine existence is exactly why encounters with people are uncommon. Sea snakes are generally not aggressive toward swimmers or divers, and most serious bites happen to fishermen who handle the snakes while emptying their nets, when a trapped animal is grabbed by hand.

All 30+ species in this genus are venomous, and the venom is potently neurotoxic. The Beaked Sea Snake in particular is responsible for a large share of the serious sea-snake bites recorded across the region. A worrying feature of these bites is that they can be nearly painless at the start, with little swelling at the wound, so the danger is easy to underestimate before neurotoxic symptoms begin to set in.

Treat every sea snake as something to look at, never to touch. Do not handle a sea snake found tangled in a net or washed up on a beach, even one that appears dead or sluggish. If a bite occurs, regard it as a medical emergency: get the person to a hospital straight away, because the serious effects of the venom can be delayed and proper treatment relies on hospital care and antivenom.