There is a "swim test" which must be passed before you can take tuition. I would suggest that you contact your nearest dive school and at least do what you are able to and improve your swimming as much as possible. Being under the water in the Caribbean is so wonderful that it is worth putting yourself out to get to that stage. But to really enjoy even snorkeling you have to be happy with and in the water...Good luck ...Neil Dow.
If you can't swim I guess you will beat all the others to the bottom of the ocean......
Lean to swim first before you think about scuba diving.