Although I have yet to be in Key West, I have a co-worker who goes twice a year, with and without his family. His advice was to do a snorkeling excursion whereby you get on a boat and they take you somewhere. However, that being said, he has snorkeled right on Key West at Ft Zachary State Park. He said the snorkeling was OK, but not similar to what a boat excursion would be like. I have called Ft Zachary and the park ranger said that snorkeling would be decent "right behind the seawall". From looking at my map, there are about 4 seawalls on the Atlantic Ocean side. The park ranger also said that if the winds were blowing from the South, visibility would be greatly reduced and snorkeling success would be extremely limited.
My family will be there on April 27th and am planning to try snorkeling at Ft. Zachary. Our youngest child is 3 yrs old so that puts the kabbash on any boat snorkeling excursions. Hopefully the weather cooperates.
I had called around initially (back when I thought my 3 yr old would be in the Disney Club), and found dozens of snorkelling tour operators. Shirley Nelson Brown, originally from Key West and a regular poster here on the boards, is very helpful with Key West information and can suggest specific operatiors.
Good luck.
