I'm relatively new to spearing in the Gulf, and when it comes to spearguns being used in the Ocean, the "Bigger is Better" philosophy is true, but maybe what I learned (a lot from the great people here on scubaboard as well as spearboard, and spearfishingworld) can help you some. Mako guns are great, I shot one borrowed from a friend when I was visiting in Hawaii. The places that sale guns will advertise them as effective up to 15-20 feet, and I've even seen one place claim 28' on a 37" gun which I just don't beleive. The best rule of distance is plan to not shoot any further than 2-3 times the length of the shaft. Another thing to remember is to buy a spear tip which is good for the fish you're hunting. At first I was shooting catfish with a rock-point, but when I went to the Ocean, I was embarassed since I wasn't getting good penetration on fish, and lost two before I realized how to work around it. For big snapper, grouper, and AJ's, a tri-cut tip will work well. That's just the basics though. I'm sure there will be someone who will dispute something I said, but hopefully it will help you.
