Mexico, Cozumel

Cozumel is an island off the coast of Mexico famous for snorkelling and Scuba diving. There are hourly ferries to/from Playa Del Carmen on the mainland. Some take 45 minutes, others 30 minutes but both cost US$11 each way. We took the Ultramar ferry which had a nice air-conditioned cabin.
You can buy tickets at the jetties.
Cozumel town itself is not very interesting but has the great Museo de la Isla de Cozumel all about Cozumel's history and info about the island.
We did a days diving with Studio Blue which were reputable and safe. It cost US$66 for two dives with all equipment rental. Water and fruit is served on the boat but its worth taking some sandwiches or something for lunch.
There´s a big supermarket down Ave Benita Juarez about 5 or so blocks away from the Plaza Mayor.
There are lots of touristy restaurants around the square. All meals get served with salsa and a huge basket to tortilla chips. You can easily share a meal to keep costs down.