My husband and I went on the Fiesta Party Boat in Cozumel a couple of years ago. Lots of fun, live band playing party games. Bottomless rum punch and margaritas. By the time we got back, the folks on board were really living it up.
The beach is nice although the tour operators take you on a jaunt through the kiosks and a very small zoo area when we went. But it only took a couple of minutes to get through the vendors trying their best to get you to buy their goods.
All in all, I'd go on it again.