My first visit to Cozumel I did the Tulum tour through Carnival. It's amazing if you are into history, but know that it is an all day thing. Almost your whole day in port is taken up by this because of a fast ferry over to the mainland, then a bus ride to the ruins. An amazing experience and I am glad I did it, but I doubt it is one I will do again.
Second visit to Cozumel I did the Beginners SCUBA. This is basically PADI's Discover SCUBA. It was a legitmate open water dive but design for those not certified yet. I also booked this one via the ship. The local provider is/was Sand Dollar. Very professional. Felt quite safe and secure the whole time and it was amazing. For this excursion we were offered pictures after the fact. At the time it was 12 each or 2 for 20, so something to consider taking cash for. Also there's a small bar where you can have an after dive snack or beer, and I used cash for that as well.
No experience with Progresso, so I will leave that to others on the forum.
Disney Dream - Dec 2012 4n Bahamas
Carnival Imagination - Dec 2011 4n Western
Carnival Imagination - Nov 2010 4n Western
Costa Atlantica - Dec 2009 7n Eastern
My opinions are mine and mine alone. They do not represent the opinions of The Walt Disney Company nor any of its subsidiaries.