Goa offers multiple dive locations a few kilometres away from the coast. There are islands near which one can dive, one even with a sunken boat. There are various companies that offer PADI certified diving courses as well as just fun day diving trips. One can even just do snorkeling whilst the others are diving.
Some of the well known ones are Barracuda diving in Baga www.barracudadiving.com , Dive Goa in Candolim www.divegoa.com and Goa Diving in Vasco www.goadiving.com.