The primary gateway between Cozumel and the mainland of the Yucatan Peninsula, including Cancun and the Riviera Maya, is the passenger ferry from Playa del Carmen. Thousands of tourists and locals take the 45 minute ride to or from Cozumel. It’s very easy, and runs nearly every hour.

http://www.cozumel-tours.com/cozumel-ferry-schedule.htm