Dressel Divers will provide transportation from your resort to their location at their Iberostar resort. Convenient because they provide transportation, are easy to work with, friendly staff, and well organized. The negative is that the dive times are limited to about 45-50 minutes (staying on a schedule) and the transportation back to your resort leaves pretty much at a set time. If you get back early from a dive you may have to sit around on the beach a bit until the ride arrives. Package deals are available on their website which can include going to Cozumel, a cenote, and a night dive.
The other way to do it (assuming you don't have a car rental) is to take a taxi to another dive op which you can find several doing a search or by waiting for others to respond to this thread. I'm limited on diving along the mainland coast, have only been along Playa del Carmen up to Puerto Morelos, but Puerto Morelos has a protected marine area and I enjoyed the diving a lot there. It's probably a 20-25 minute taxi ride from your resort.