Helveticosaurus is a reptile with a short snout, long sharp teeth and a body about 2 meters in length from snout to tail. It was adapted to the marine lifestyle in shallow water that existed in Europe about two and a half hundred million years ago. The long, flexible tail of Helveticosaurus is similar to this part of the body of other extinct marine reptiles and it probably moved through the water, creating side waves. However, Helveticosaurus also possessed a robust pectoral girdle and forelimbs that were well adapted for paddling. This unique combination of the tail and paws is very unusual for an aquatic reptile.

All remains of Helveticosaurus were discovered in the bitumen layers of the mountains of Swiss Canton of Ticino, where more than 240 million years ago the majestic European Tethys Ocean was. Helveticosaurus lived in the shallow waters of the sea shelf, where it caught fish and mollusks. Its body was adapted to life in the water, and it allowed Helveticosaurus to go ashore.