This is a real fact that the sea snakes like Hydrophis belcheri are most poisonous snake in the world. This type of snakes occur mainly in the warm tropical waters & its a part of the elapids group of snakes.The sea snakes feed mostly on fish which they swallow whole. These snakes have laterally compressed tails used to propel them through the water, nostrils with valve-like flaps which can be closed upon submersion, and lack any ventral plates.