Water snakes are scavengers and carnivores, eating prey such as amphibians, crayfish, other snakes, birds, small mammals, fish and large insects. These snakes search for prey during all hours of the day and once they catch something, they just swallow it alive.

Larger snakes, such as racers and milk snakes, tend to prey on water snakes. However, they are excellent escape artists because they can discourage attackers by defecating or emitting a foul-smelling musk. They have the ability to flatten their jaws and bodies, making them hard to see. They are able to stay underwater for up to 5 minutes to hide from predators.