I’m not a fan of snakes (蛇 or へび) per se, but I do find it interesting that they have developed to live both on land and in the sea.
Sea snakes (海蛇 うみへび) tend to have a paddle like tail end to allow for better movement in water. Several species can hold their breath from 2-3 hours when feeling endangered (and thus avoid going up to the surface for air). Also, nearly all species of sea snakes don’t lay eggs after mating, but rather the young grow in their mothers’ wombs until they are ready to be delivered.
Source: 10 Amazing Facts About Sea Snake Which You Must Know
Here are some pretty cool sea serpents! ^>^
Belcher’s sea snake (ベルチャーウミヘビ) - this one is extremely poisonous, but is actually quite good-natured. You’ll have to really provoke it for it to bite you (which you shouldn’t be doing! 
)
Olive sea snake or golden sea snake
Yellow-bellied sea snake (背黒海蛇 or せぐろうみへび)
Going at it… 
