Tulum is a FABULOUS tour, but you'll see little else of Cozumel if you go. Besides the ferry to/from the mainland, the bus trip is considerably longer than 45 minutes, in fact, it takes that long to get to the jewelry factory/rest stop and at least that again to get to Tulum. We did Tulum our first trip to Coz and booked another trip cuz we never saw Coz. Also, Playa del Carmen, where the ferry lands, has a GORGEOUS beach. Here's a couple pics of the ruins and the beach below.