Most of us cant drop 500 dollars on a harpoon. Its a video of how I made mine. Its better than not having one and has worked well for me the times I have harpooned swordfish over 200 pounds. I have 100 feet of rope then connect the end to a 50 wide.
Small tuna head $31
newenglandmarine.com/product/...
Shank $7
newenglandmarine.com/product/...
Bronze Dart $14
Aluminum Pipe sell in sections of 12 feet ( 1 1/4inch) $12
100 feet of 1/4 braided line $ 9
PVC 16 lb buoyancy float $10
Aluminum rivet for head to pipe. (another material with cause electrolysis)
Optional is the Clip at the back