The olive sea snake is perhaps the commonest true sea snake in the tropical waters south of Papua New Guinea. It inhabits coral reefs and rocky coastlines to depths of up to 45 metres.

The upper body is purplish grey or dark brown, and the head light to medium brown. Commonly, though not always, there are creamy scales along the body. The head is short and of equal width as the stocky body. The nostrils are valved, thus preventing water ingress. The tail is paddle-shaped with a raised ridge running along its length. The eyes are small.

As with all true sea snakes, live young are born at sea. Adults need to surface every half an hour to breathe fresh air. The species feeds on fish and crustaceans, and is active both day and night.

Sea snakes are highly venomous and should be treated with caution, though in reality they are generally not aggressive in temperament. Bites from the olive sea snake are rare.

The olive sea snake occurs in the Timor Sea, throughout the northern and north-eastern coasts of Australia, and in the Coral Sea and other areas south of Papua New Guinea.