Supposedly SCUBA divers occasionally knife flatties. I haven't heard of freedivers or spearos doing this but I expect some do (or used an unloaded spear gun or pole spear). I purchase a steel crab hook sometime ago that can be pushed back through the handle to reveal a "fish spike" -- presumably for spiking flatties?
I wouldn't use a $130 knife for diving though (gold & silver Rambo knife?
). I think a crab hook/fish spike costs about $10/£5 (from Portland Oceaneering). Plenty of dive knives about for under $20, most are decent and some very good. Or pick-up some old kitchen knives (or ski poles) at a local charity shop, or use your knife to make a pointy stick!
