they eat little fish
NO! Leatherback turtles. Are specially adapted to SALT WATER. They would not survive in freshwater. Also, the grasses that they eat are adapted to salt water. So, they would have the wrong water, and the wrong food. That would be like living in Carbon Dioxide and having only glass to eat.
Snapping turtles
Box turtles live on land not in water
Snapping turtles live in fresh water
If snapping turtles have salt the tongue of the snapping turtle will dry out and the turtle will have no interest to eat.
Salt only.
The saltwater crocodile will basically eat anything it can get in its jaws. But for the most part they eat things such as snakes, birds, fish, turtles, crabs, lizards, and crustaceans.
maybe
yes, all water turtles do
Painted turtles eat fish, worms, insects, water lettuce, water hyacinth, and duckweed.
Salt water crabs Salt water lobster Sea otter Sea turtles
A clue is in their name - sea turtle - sea is salt water.