Although this post is a long time coming... I have not had time for spearing in awhile, and have not checked this forum...
Anyways.
You need florida regulations, and salwater license.
You need a dive flag. If you bring a yak, you need a bigger flag. (see regs)
You need to know what you are shooting, and the regulations pertaining to what you are shooting. Remember that fish look bigger under water than they really are. If you think that they are close, or just barely legal, don't shoot them. Check regs for specifics on size and catch.
You need basic free dive equipment. To start with, you can go with anything that you want really. Fins, Mask, Snorkel, Gloves, Belt, and Weights. ( I like a wet suit, but not needed if water is warm.)
Dive knife. A pointed one. If you don't kill the fish with your shot you will need to knife him in the brain. Don't stab yourself... I have.
Speargun / Spear Pole / Hawain Sling -
Speargun - Depends on what you are shooting. Starting out? Boatless? Yakless? I would personally get something small, a "reef" speargun. 100m You can go big if you are going blue water, or planning on spearing monster fish off of wrecks, but since this is boatless fishing, I am thinking beach swims out to shallow reefs.
Spear Pole- The big yellow ones you see at dive shops will do the trick for small fish. If you want to spear something bigger you will need better spear poles with interchangable single prong tips. There are really some cool ones if you look around.
Hawain Sling- I suck with these. Everyone I know sucks with these. If you are a serious bad ass, roll with one of these, and watch your buddies slay with their spear poles and spear guns.
Shallow Water Blackout*- Do not hyper ventalate or try to increase oxygen in your blood by taking a bunch of large breaths before diving. You can trick your body into thinking things are all good, when really your oxygen is gone. The result is you blackout immediatlly, and drown. Read up on this. Not to be played with.
http://scuba-doc.com/latenthypoxia.html
Get a map of the reefs, or head out to Oakland Park blvd, and find a beach. Swim way the hell out and find a reef to harvest on. I use a yak now, but in the past I swam out.
Always bring friends. Don't go out alone. Don't go iff you can't swim, or you are out of shape. Do more research. Don't break the law. Don't piss off fisherman. Stay away from the piers, it is illegal. If in doubt on regs, ask or call someone with fish and game.,