It's not often that I say this, but I think this is one of those times where you should pause, listen to what people are saying here, check their experience levels diving in Coz, and think this over again. Because this is experience talking. These comments are being made with your safety in mind...both in terms of accidents that could happen in the water and DCI risks. I have only once tried to do a dive the day I arrived (on the Big Island). It was a bit of a gong show and my husband got pi***d off at me for a few days afterwards. Christi has given you a really good option here. BTW, I dive AND snorkel in Cozumel. But on day 1, I like to check out my accommodations, renew acquaintances with folks there I know, have a nice dinner, stay nice and hydrated, go to bed early and be well-rested for my early wake up call in the a.m.