Adult male sea lions are huge - up to 350 kilograms, more than three grown adults put together. They have thick golden manes around their heads, a little like lions on land. The females are much smaller, and the pups are tiny - about the size of a small dog.
Sea lions are made for the ocean. They have streamlined bodies and flippers that work like paddles. Underwater they can twist, turn and chase fish at high speed - they can swim at 30 kilometres an hour and dive 200 metres deep. On land, they shuffle along on their flippers in a slow, comical waddle.
Isla de Lobos got its name from the Spanish words 'lobos marinos' - 'sea wolves'. There are no real wolves on the island, just an enormous, noisy crowd of sea lions sunbathing on every rock. The colony has been there for hundreds of years and is protected today as a wildlife reserve.
Closer to shore, sea lions are a very normal sight in Uruguayan harbours. In the busy port of Punta del Este they doze on jetties, beg for fish scraps from fishermen and sometimes hop onto the back of a moored boat for a nap. Locals walk past them as though they were the neighbourhood cats.