Whether living or ancient aquatic reptiles, their ancestors all lived on land. But if you look it further, the predecessors of their land-liv- ing ancestors were again water-dwelling. In late Devonian of the Paleozoic (about 354Ma), some aquatic animals landed to expand their habitat. After that, some terrestrial animals returned to the water one after another, including aquatic reptiles and mammals such as cetaceans and dolphins. From the "fins" in the water, they evolved into "quadrupeds" after landing, and then transformed into "flippers" when returned to the water. The mystery of evolution is amazing.

Many lakes and rivers around the world have legends of monsters, the oldest of which should be the Japanese water monster-Kappa, and the most famous one should be the "Loch Ness Monster" in Scotland. The legend of Loch Ness Monster can be traced back to the sixth century A.D. In 1934, the British Dr. Robert Kenneth Wilson showed his pictures of Loch Ness Monster, which made the rumors of Loch Ness Monster even more sensational. Although this photo was not very clear, it still showed the image of Loch Ness Monster in people's minds: with a long neck and a flat and small head protruding from the lake, it looks like a species of Plesiosaurs that went extinct more than 70 million years ago.