One of the biggest things people want to do is snorkel while they are in Costa Rica. Zipline, Whitewater raft and snorkel. You think tropical location and you think snorkeling, but I found that Costa Rica didn't quite have the brilliance of the Caribbean or the up close Encounters that I've heard of in the Galapagos. I wanted to be sure to snorkel on both the Caribbean and Pacific sides to see if one was better than another. In my honest opinion, as far as the snorkeling was concerned. Not a big difference. I do think the Pacific Side one out by a hair for one reason though, Cano Island.
To say my trip out to Cano was torturous might be overstating it a little, but it was very, very uncomfortable. Luckily my experience is not all that common. We went out in a downright storm, for one thing. And I was the only one going out so our boat did not have the wight it needed to ride the rough waters easily. Despite the rough trip the snorkeling was a success. Even in the rain I saw incredible fish and beautiful coral. Since the island is so far from the shore the waters are traditionally much calmer which makes for those idyllic calm waters that make floating an watching the fish swim by a much more enjoyable venture. To save on the long boat ride you are better off taking this tour from Drake Bay as opposed to Ballena, where I came from. On the positive side we did see Sea Turtles and spotted Dolphins on our boat trip so that kind of made up for it.