You might want to check out the
Cozumel forum since that question has been asked hundred of times before. Ask again and you'll probably get a hundred more answers based on what everyone else likes. It may not necessarily be what you'll like. Your choice depends on your personal preferences. Some of the variable are...
- large boats or small boats, fast boats or slow boats - not all large boats are cattle boats or slow, and not all small boats are fast or comfortable, so don't get sucked into the cattle boat vs fast boat sales pitch. Fast boats can be a rough ride and not all offer any protection from the sun, weather or seas, most don't have a head, but they will get you to the reefs 20 minutes before the bigger boats, if for some reason you're in a hurry.
- if you like to meet other divers or prefer to stay to yourself - I like the bigger boats for many reasons, but one is because I meet a LOT of really nice people in Cozumel. Big boats have a number of different areas you can congregate to so you can mingle with your choice of people if you want, or avoid the ones you don't want to be around. The big boats I've been on are all quieter than the small boats, so you can actually carry on a conversation with someone without shouting into their ear. Several times I've been on a six-pack boat and got stuck diving with the loud, obnoxious, know-it-all diver with no escape until I got off the boat. Doesn't make for a pleasant trip.
- how much diving you're planning on doing - most ops run two-tank morning dives, some leave earlier to get back to do afternoon dives too. Others leave later and stay out most the day. Some will even do full-day three-tank trips if the whole boat wants to do it. I've done that a couple of times with Aqua Safari. They all have different dive schedules.
- if you plan to do shore diving - Dedicated dive resorts like Scuba Club Cozumel have free unlimited shore diving for their guests, or you can do optional afternoon boat dives and night dives. Their shore diving setup is the best I've seen in Cozumel.
- where you are staying - most dive ops pick you up right at your hotel, but not always if you're staying north of town. Some resorts have dive ops on site.
- if you prefer an all-inclusive or rooms/meals/diving package or want to pay for it all separately. A-la-carte will be more expensive if you plan to eat all your meals at different restaurants each day. With the exception of Scuba Club, the all-inclusive food got repetitive after a couple of days.
- how much money you want to spend
That said, I've dived with many different operators in Cozumel and like or dislike them for various reasons. If you're an advanced diver and want to dive in a small group you might like
Mestizo Divers. They have a very nice fast boat that has a head, cabin, shade from the sun, protection from the wind and splash and an experienced first rate crew. Prices are competitive and they'll never take more than six divers. Another shop you might like is
Deep Exposure Dive Center. They have a bigger boat that is also very nice and the crew is fantastic.
Aqua Safari has larger boats that can carry more divers, but I have never been on any of their big boats with really large groups and I've dived with them hundreds of times. They also have a great fast boat named "Belinda" which is a great boat with one of my favorite boat captains in Cozumel. The staff at Aqua Safari is excellent too. Scuba Club Cozumel is another one of my favorites. They have the best of everything and I always have a great trip when I stay there. I've also heard good reports about Aldora Divers and Blue XTSea, but have not had the opportunity to dive with them.
I've also been diving with lousy operators who I will not mention (so to not start a firestorm). I'll just say that just because someone does a lot of advertising, that doesn't mean they are a good dive operation.
Stay for a couple of months and dive them all.
Hope this helps!
