Snakes that swim.

Cottonmouth snakes, which are venomous and dangerous to humans

King Cobra. They like to live in forests and near water. They can swim well and can move quickly in trees and on land. And they won't retreat back when attacking you even on water.

Python.

They are also excellent swimmers, and can stay submerged for up to 30 minutes before surfacing for air. They won't also think twice about striking.

Water Moccasins

Fights back when attacked. Fat body but moves swiftly on water.

Tiger snake.

Found in Australia. Another land and air (tree) snake. Fights you to the last minute. Best man wins.

Gaboon Viper.

Found in Africa.

2nd most venomous and dangerous snake after King cobra. You don't wanna get face to face with this one at the river

Russell's Viper

Restricted to any particular habitat, but does tend to avoid dense FORESTS.. Found in Asia particularly India. Goes on water after you when provoked

The Notorious Black Mamba.

Contributes to many cases of snake bites in Sub Sahara Africa. Moves swiftly. Fights aggressively.

Anaconda

Sema aquatic. Less likely to attack a human. But I guess you don't wanna have a meeting with it.