Swimsuit for open water

Hello all. What kind of suit is good for open water? I searched and found few topics about but it didn't clear much. Is it like sailing suit or trisuit? Or wetsuit like divers have? I doubt that regular race suit with long legs help to keep body warm. I googled some suits also but I didn't find suits just for open water swim. Except blueseventy homepages but suit was too expensive.