I booked through cozumelinsider.com. They had several options with different prices. Make sure you do the swim and not the encounter. Good luck.
Celebrity Century 1/09
Carnival Destiny 10/07
Carnival Destiny 9/06
Monarch of the Seas 3/06
Carnival Inspiration 8/05
Carnival Miracle 4/05
Carnival Inspiration 4/04
Sovereign of the Seas 4/03
This is just a copy of what I posted earlier in the HAL board in response to someone who had a question on excursions. Feel free to email me with any questions you might have...
Cozumel: We had the most fun of the whole cruise on this excursion which we planned on our own - the dolphin swim. Here we contacted www.dolphinsdiscovery.com and booked with them directly. We choose the Royal Swim - $125 per person. Yes, it's expensive, but totally and completely worth it. By doing it, you get to hug a dolphin, kiss a dolphin, shake "hands" with the dolphin, have 2 dolphins pull you around (the dorsal tow) and have 2 dolphins swim under you and "raise" you by your heels - which makes you look like you're waterskiing without the boat or the line! Total costs:
Taxi from Cozumel port to Chankanuba Park: $10
Admittance to Park: $12 per person (adult)
Fee of $125 per person to the dolphin discovery place
I'd recommend booking an early time to do the dolphin swim. The park itself is a park and a beach. They have lockers and facilities all over. It was VERY well done. We did the 10:00 swim. It was just so hot that we ended up leaving the park early b/c we wanted to do some shopping and get back to the ship.....