Snorkeling and Scubadiving

I´m planning a trip to Sosua in july. I´m very interested in snorkeling and are thinking about to maybee take a course in scuba diving.

Where is the best place to go snorkeling, what does it cost to rent snorkeling equipment (my own is to heavy to bring in my travelluggage)?

I´m also would like to know where the best and cheapest place are to take a course in scuba diving in Sousa.

/Ina