I just went on the similar cruise a few weeks ago. The cruise is as typical as any, all the free food you want, but you get a card you just swipe liquor, so be careful, the prices are insane. I spent over $500 for alcohol alone, my GF loves those fruity drinks and they were like 10$ a piece and beers were around 7$.
Swimming with dolphins was amazing, but extremely sketchy at first since I have the worse fear of sharks but they say sharks tend to stay away from the area due to dolphins. If you do snorkeling prepare yourself to be within 50 feet of sharks....... You get over it real quick, or you have a panic attack lol.
Depending on your schedule, the hikes around Cozumel is super cool, lots of old shit to see.
The surfing was ok, but nothing to brag about, I live in Florida and I prefer the swells here if that says anything.
The night life/club scene isn't bad, just not my thing, since I hate dancing but my girl loved it.
It really is a sweet place considering the price,
DO NOT TRY TO BUY LIQUOR FROM ANY PLACE AND BRING IT ON THE BOAT...... They WILL find it and make you leave it... even if the bottle was VERY Expensive...