sharkie sharkie sink!

Perhaps surprisingly, if a shark stops swimming, it will sink. Most other fish have gas-filled swimming bladders to help them float, but sharks have to rely on their oil-filled livers to give them buoyancy. The livers are not enough of a floatation device, however, so the sharks must swim, or they'll sink.

walkie fishie?

There are some types of fish that can indeed "walk" on land. One is the walking catfish, which uses its pectoral fins and tail to move from pond to pond.