The Belcher sea snake is currently recognized as the most venomous snake species in the world, many times more venomous than land snakes. Belcher's sea snakes are mainly found in the Indian Ocean. Inhabits the coastal waters, especially in brackish estuaries, and feeds on fish. Belcher's sea snakes are similar in shape to land snakes, the biggest difference being their side flattened tails. Belcher's sea snakes are all venomous, but their heads are mostly oval rather than triangular, similar to non-venomous land snakes.

Belcher's sea snakes are venomous snakes that live in seawater all their lives. Belcher's sea snake's nostrils face upwards and have valves to close back. After inhaling air, they can close their nostrils and dive underwater for up to 10 minutes. The body is covered with scales, and beneath the scales is a thick layer of skin that prevents the infiltration of seawater and the loss of body fluids. The salt glands under the tongue have the function of expelling excess salt that enters the body with food. The small Belcher's sea snake is half a meter long, and the large Belcher's sea snake can reach about 3 meters.