Anyone ever tried using a carbon shaft for spears? If so, where would you get them?

It seems that the fexibility would sure be there.

not sure if they are comm. product but tried them in late 90s they are way too light for the speargun to have any use no velocity like an arrow and too light to penetrate very well

Are you talking for fish or wild boar? I'm guessing you mean hand-held instead of from a speargun. I use a 3 prong 7' solid carbon graphite 7/16" diameter Hawaiian Sling style spear with attached surgical rubber sling for reef fish. I found these superior to the heavier 5/8" solid fiberglass spears for daytime shooting where speed is an advantage. At night for larger game where speed not as important as weight for better penetration. If you are talking a boar spear shaft i'd go for heavy duty so fiberglass over carbon-fiber.