In the bad old days some uncaring folk used to put a .303 or a well waxed shotgun cartridge into a suitable holder with a well positioned spring loaded firing pin and mount the whole thing on the end of a hand spear.
One twist to lock, reverse to unlock.
Some of the more chicken individuals used to mount it on the business end of a spear gun.
Aparently sharks like to do a few close circles before dinner.
I believe they are banned now, but could probaly be found on ebay(everthing else seems to be there).
Some of the more daring individuals used to mount three four inch nails on the end of a broom handle and poke the result at any creature that came too close.
This might all belong in the same category as the story about the poor soul who wore a red lined wetsuit inside out.
It used to be said that one had a better chance of being struck by lightning
than being atacked by a shark.