And when you thought we had seen them all: Sling Fish.
It's an american brand based in Florida, offering type of monococque Carbon fiber guns. They look like beefed up C4, similar in look to greek Bleutech guns.
Their website speaks of an "internal ballast sysstem", but it's unclear to me how it works. is it water ballast? Dunno. Here they are. First american carbon monocoque I've seen so far.
Click on the Mohawk menu selection here speargun
Looks like something similar is being cooked up in Asia!