Olive sea snake. Close-up of the head of an olive sea snake, Aipysurus laevis, among rocks on the sea floor. Sea snakes are related to land snakes, but have adapted to a marine existence, including a paddle-like tail (not seen), a flattened body and nostrils which can be closed. Being reptiles, sea snakes must still surface to breathe, but can hold their breath for up to an hour. Sea snakes generally feed on fish, injecting a paralysing poison with their fangs before swall- owing the helpless prey whole. The olive sea snake corners fish in crevices before killing them. Photographed on the Ningaloo Reef, Australia.