The snorkeling in the Gulf of Mexico is very limited in how far you can see (visibility) and what there is (reef/structure) close to shore. The Gulf has a mostly sandy bottom, so unlike the Keys and Caribbean, there isn't much natural structure and habitat that holds life.
Our local beach areas have sand dollars, shells, and a few species of fish that can be seen if the water is fairly clear (walk in up to your waist and still see your toes). In Naples there is a small patch reef (soft corals and sponges) at Wiggins Pass Park. The depth is around 15 feet and the visibility is generally less than that. You can't (usually) see the bottom from the surface anywhere in this area, so that hampers taking snorkelers on our dive trips as most of the marine life is near the bottom. Although there are times when the water is clear along the shoreline, it's not the 'norm' for around here.
We do rent and sell snorkel gear and can suggest a couple places to go when the clarity is good along the shoreline. Snorkeling instruction for beginners in a pool is available, call the shop for details. We also offer Discover Scuba lessons for non-certified folks at least 10 years of age. We start with a video and pool orientation then do a boat or dock dive locally. (See Discover Scuba page) Getting away from shore to our local artificial reefs and wrecks improves the visibility to generally 15 feet or more, which is enough to see the high concentrations of marine life here. Our area is a breeding ground for Goliath Grouper which are very common, many are over 200 pounds!