Underwater mudskippers look much like other fish. But the mudskipper can also shuffle overland using two pairs of modified fins. This is how we once thought backboned creatures left the water. We now know that legs actually evolved for use in the water. But how? The oceans are home to other bizarre creatures that appear to walk across the sea bed. Rosy-lipped batfish never leave the sea and are perfectly good swimmers, but they also use their fins like pairs of legs. By stalking prey on stilt-like feet they do not stir up water or sand and so do not alert their prey. The frogfish has also evolved two pairs of modified fin-feet to help it navigate the nooks and crannies of the ocean floor. But evolution did not really run with the idea of feet until around 370 million years ago when the climate changed.