Hi,
I was diving in Cozumel last week !! There was a lot of current there, and the water was very warm. Easy dive in my opinion.
But, you must dive in Isla Mujeres, In my opinion is far away better than cozumel. Just take a boat from cancun and 20 minutes after you are in Isla Mujeres...a lot os fishes and corals there
My wife did her first dive in Cozumel, no problem for beginners. The current is good, you don´t need to make a workout to dive
Just relax and enjoy
Good luck and enjoy cancun and cozumel !
Regards