As far as I know, there is only the dolphin swim at Chanakaab Park in Cozumel, check under Dolphin Discovery. You can easily pre-book this yourself and take a cab over, its not too far from the port.
Carnival has tours going to the Dolphinaris in coz. From the website it looks like you can get much more time with the dolphins than at dolphin discovery. I am looking for anyone who has been there. WWW.dolphinaris.com Let me know if you hear from anyone who has been there.
We actually did the Dolphin Swim in Tortola - it was amazing - really one of the best activities i have ever done in the Caribbean - But the company we booked through is located in many of the Islands including Cozumel , Mexico. They are called Dolphin Discovery - I have posted loads of info including details of tour types/prices about the company including all website links in www.cruisegossip.co.uk - sorry but there is too much to relay here - hope that helps.