Discover scuba vs snorkling

Hello,

We’ll be in cozumel for 2 nights and staying at the presidente. We’d like to do atleast one of - 1. A 4 hr snorkel boat tour to el cielo and 2 other locations. 2. Discover scuba total 2 hours. First learn in shallow water and then go to a (shallow?) reef

I’ve heard cozumel is great for scuba. But will discover scuba be as good or is snorkeling better. I’ve heard a lot about el cielo too.