On most dives in Cozumel, you can avoid the wall with no visible bottom with the exception of a couple sites. There are many sites that you can swim out over the edge, but you don't have to.
I did my first dive in Coz on Palancar Caves. The name had me intimidated, they were more like swim throughs than caves. Just be honest about your experience and comfort level like most have said. I was given the option to stay more shallow than 80ft and whether or not to do the swim throughs. You can just drift over them if you choose not to do them. I was glad I did the swim throughs, they were beautiful!
Aqua Safari does have a small boat, the Belinda...just book in advance as she fills up quickly. Scuba Mau has great service & DMs, Opal is a gem. I can also recommend Scuba with Alison, she fills up quickly too.
Have fun & be sure and let us know how it went!
