Making a spear gun shaft includes selecting a solid steel drill rod of desired length; wrapping the rod with thermo-setting polymer impregnated carbon fiber sheet; covering rod with compression wrapper; curing the resin coated rod in an oven; removing the covering; machining the cured resin to the desired diameter with ends exposing drill rod; affixing a spear tip-carrying member to an end of the rod; affixing a trigger-engaging member to opposite end of the rod; affixing collars over the joints formed between rod and members to reinforce the shaft at the respective joints; mounting a sliding collar onto rod; and affixing the collars with metal adhesive to waterproof and seal the respective joints covered by the collars.