Sorry no one answered you yet, I didn't know where "south beach" is. But spearfishing is spearfishing, anywhere. First you need to start above water, look into state laws about what you can shoot, seasons, licenses and dive flag regulations. Now that you can avoid arrest, Learn what local fish are good to take.
Once you know what fish to hunt, ask at a local dive shop, what equipment is best suited to your target. Short range, thin skin can mean a short one band speargun, or polespear.
Medium range would suggest a medium length gun, There are a lot of brands with prices based on quality of materials, and amount of hand work. JBL is a moderate price gun manufacturer, they offer several guns like the 38 special with two bands and a 38 special NW with 3 band slots in the spear.
Long range can best be hunted with a long gun. Lots of custom manufacturers are making guns for big fish at long range. Which gun at what price is a never ending discussion on any spearfishing forum.
In learning to spearfish, nothing is more important than lots of time in the water. New divers scare fish further away than they can see the fish. With lots of bottom time, your breathing will slow down, and if you also cut down on the flailing arms, wide bouncing around because of no buoyancy control you will be able to get closer to all fish.
If you haven't already learned to approach fish for spearing, learn by practice to swim with the small food fish. Your underwater skills progress from scaring everything, to swimming with the bait fish, to swimming along side the target fish. Learn from the Shark videos on TV, Sharks swim among fish, without disturbing them, but as soon as the shark turns toward and singles on one fish that fish will run in fear. Good spearing technique is to swim at an angle to your target, not straight at it. Then when in range, shoot at an angle to your body. Fish react to a predator fish facing straight at them and biting, they don't have a fear of a large object swimming at an angle, and harming them at an angle to them.
Keep asking questions, and you'll get an answer. . . just keep the question more universal, and there are lots of people that can answer.
