dlndavid:
Just curious Ken, what would be the appropriate weapons? I like having the upper hand.
Them Tigers sound pretty scary.
David
After simply noting that any powerhead/bangstick is a firearm and handling one absolutely requires the same respect and responsibility, I'd say that the two most effective anti-shark weapons were the Farallon SharkDart and the AquaCraft/Rhett McNair Fastload, both of which were developed during the powerhead mania of the early 70's and have long been unavailable.
The SharkDart came in several sizes, the smallest being about the size of a dive knife and worn similarly. SharkDarts were simply super-duper hypodermic needles backed-up by a screw-in CO2 cartridge, either 12, 16, or 25gm. The idea was to penetrate any body cavity and instantly inflate the animal. This resulted in at least getting the animal away and nailed to the roof. The theory was good and the demonstrations impressive. The Dart's weakness was the fragility of the hollow needle; it was a hollow steel needle with a hardened point with gas ports just behind it. Getting adequate penetration into the body cavity and the gas discharged before the animal went berserk was also problematic. I've handled the device but know of no one who actually used it.
Rhett McNair was living in Kailua, Oahu when he invented and patented the Fastload. Complete descriptions and diagrams of it can be seen on the U.S. Patent Office website; look up patent #3747247. The key to the Fastload was the special cartridge which was the mating of two straight-walled rifle/pistol cases; I think it was a .30 carbine or 30-30 mated to a .38 Special. The idea was that underwater destructive power came more from the explosion of gas than the penetration of a projectile. The weapon was used just like a regular bangstick. The uniqueness of the Fastload was that after detonation, the entire cartridge was instantly expelled and another could immediately be inserted without having to unscrew or disassemble anything. It was hellaciously effective; I believe that a picture of one in action may be seen in the small book "Sharks of Tropical and Temperate Seas" by R. Johnson. Like any bangstick, the target areas are the jaw joint or just forward of the dorsal fin. The Fastload failed as a product mainly because of its ammunition was just too unique; cost and availability doomed it.
Frankly, I do not miss these products since they are extremely dangerous and therefore useless to the recreational diver. I do acknowledge that they may have applications as defensive tools in commercial or scientific scenarios. The best anti-shark weapon costs nothing and is located between your ears.
p.s. Giant groupers or jewfish (in the 500lb range) have been seen and fished from Hawaiian waters. They tend to live in the very deep dropoff reefs but are occasionally seen by sport divers in shallower waters. It is believed that these fish are more oceanic strays rather than a resident population. The roi or peacock grouper is the most commonly seen; it's an import. A larger endemic grouper (up to 50lbs) is sometimes seen.