Do they have Snuba where you're going?
http://www.snuba.com/about-snuba/
Getting certified is expensive, and you need to buy mask/snorkel/fins/booties, too.
If the only time you'll use it is this trip, it'd be an expensive thing to do.
I got certified when we lived in SoCal - went diving a bunch. Last time I went Scuba diving was in 1990. Many snorkeling trips since then.
Don't get me wrong...Scuba diving is cool (especially night diving!), but if you don't live where you can go pretty often, it's a lot of time/money for not much return on your investment.