I snorkeled for the first time in Oct 2009 in Bermuda. The first time was on one of those guided tours (cruise excursion). When I saw how easy and amazing it was I bought a cheap mask and snorkel set at a drugstore and hit the beach myself.
The second excursion was even better than the first, Warwick Long Beach on the south shore. I saw dozens of very large angelfish, parrotfish (Blue, Queen, and Stoplight), as well as many species of damselfish and butterflyfish. It was an absolutely perfect day.
So, on the third and last day we were docked I went to the snorkel "park" at the Royal Navy Dockyard. The water was not as clear (winds were higher, and there were more people in the area), but there were lots of fish--Sergeant Majors, Yellowtail Snapper, and I even saw a Longspine Squirrelfish!
At one point I was surrounded by hundreds of Bar Jacks all swimming calmly in one direction (schooling). All of a sudden they parted (odd, because I had been swimming with them for several minutes without them seeming to notice), and I saw the biggest fish I've ever seen in my life swim 5 ft directly under me! The first thing I thought about was how every now and then you hear stories about HUGE catfish the size of Buicks at the bottom of deep lakes. I screamed in my snorkel, and swam as fast as I could back to the shore.
After getting a grip on myself, I did a little research and from what I can tell it was a VERY large (I'm confident that it was at least 4.5ft long) Black Grouper!! Too bad I didn't have a camera on me. It is an experience that I will never forget.