When we move, our legs push against the ground. Fish have fins and a tail. Fish swim. What do the fins and tail push against when they are swimming?

We walk about, and run, and skip. Animals move about. They move to find food. They move to find somewhere to live. How do different animals move? Animals on land walk or run or slither. Fish in the sea swim. Whales swim too. Birds in the air fly. Insects fly as well.