Ditto on Pennekamp, snorkel friendly,,,,kinda hard to offer any other places(dive shops) down there, since the last yrs. storm(some of them closed up), I think Hens and Chicks is another good place to snorkle. If you are going out with a dive shop's boat, check with them b4 you get there, and see where they go,,,
Nothing really right off shore to see ,snorkling or otherwise, unless you dive under the bridges, and i would not recommend it ,if you are not sure of tide times, or fisherman above/around you.(there are a wild bunch of stuff that comes/goes at tide change, but would not recommend being in the water at that time, from the current , or the big critters passing thru.)Most all diving in the Keys is done out on the reefs, nothing you can get to w/out a boat.
Find some dive shops down there, ask around and see where most of them are going to. some places will take snorkelers out with a dive group, and i think there might even be places that do snorkel only,,,(i seem to remember a catamaran trip , snorkle only that made a day of it, lunch and all:drool: but the name evades me now)
If your over 21 check out Island Marada. It is a Party place. The tiki bar is the best. There is a statute of JC that is in 20' of water I think that it is part of Pennycamp but do not remember exactly. I will see of I can Dig up a Name it been a while since I have been down there. It's a shame really I live a darn hour away for cying out loud. Also the Lorele resturaunt is great food and they usually have live music the last time I was down there they had Big Dick and the Extenders playing. (Obveously not for kids) but funny none the less.
Thanks for the info we may eaven take one of the one day dive class tee main reason we are going is for the reefs if any one has any favorite places south Fl. or through the keys most definatly going to pennekamp all with instruction planning on seeing asmuch as possible