Re: Don't know if knives can be considered part of this...
I can see some of the application as a dive knife, but honestly, this seems pretty superfluous.
And if it WAS meant to defend against a shark, it needs to be on the end of a long pole with a sling at the very least. A spear with the freeze effect might be handy.
For above the water, it just seems pointless. Be better to make a knife that once you stabbed it in the target could fire off a shotgun shell or something for work on land.
A person convinced that the ends justify the memes.