Look at my signature, there is a link to my snorkeling and collecting thread here. And there is a lot of good info there including a few good sites to snorkel off the beach.
Unless you are over 65 years old (hey, some of us are!) you need a saltwater fishing license to collect. Florida FWC has VERY strict regs on what you can and can not collect and limits even on the items that you can collect. You'd be extremely lucky to find any mushrooms or even ricordia while snorkeling. You do understand that ALL stony coral (SPS & LPS) are completely illegal to collect. Live rock is also illegal. Condy anemones are illegal. There are some zoas, and the limit is 5 polyps per licensed collector per day! Gorgonian corals are 8 colonies per day (which I think is crazy as I've seen a few colonies that wouldn't fit in my 50g tank if I stuffed it in with a trash compactor!). Snails, hermit crabs, mithrax crabs, porcelain crabs, serpent stars, brittle stars, ordinary stars, sea cucumbers, rock flower anemones, curly-Q anemones, spaghetti worms, feather dusters are all allowed. Most fish are allowed, but then most fish are really difficult to catch, even with a good net. HOWEVER, there is a 20 animal per day limit. So 5 zoa polyps, a couple small gorgonians, a few serpent stars, 10 turbo snails and you are at your limit.
And DO NOT get caught with anything illegal or over the limit. The fines are substantial. I asked an FWC ranger what the fine would be for a single stony coral and he said it could be jail time and/or up to a $2000 fine! And I've been checked by FWC rangers while I was snorkeling in the water (they were on jet skis), while in our zodiac (they were in a boat) and at the boat ramp (they were in an SUV). Take this advice very seriously.
