Passion Island unfortunatly is not worth the money. It is a private island, and the beach is beautiful. However, there really isn't anything there to do other than play volleyball and lie out in the sun. There is no snorkeling at all. They do serve you luch and give you drinks. It you can drink $75.00 dollars worth of alcohol, then go for it. You'll most likely follow that by passing out in the sand. So you'll take advantage of two of the four things they offer. Save the money and go somewhere else on your own.
As a side note, since Passion Island is north of Cozumel island and exposed to the ocean, it can be really windy.