What do snails under water eat?

aquatic snails eat algae and live plant material. if they are in an aquarium, they also eat leftover fish food.

From different user:

i had a water snail and the water snail liked to eat clover and grass. Be sure to wash outdoor plants thoroughly so that the bugs don't get in the water. Water snails also eat other things but from my experience, they eat clovers and grass.