There is a scientific explanation for all this but I'll try to keep it simple.

Our eyes are sensitive to light which lies in a very small region of the electromagnetic spectrum labeled "visible light". This "visible light" corresponds to a wavelength range of 400 - 700 nanometers (nm) and a color range of violet through red. The human eye is not capable of "seeing" radiation with wavelengths outside the visible spectrum. The visible colors from shortest to longest wavelength are: violet, blue, green, yellow, orange, and red. Ultraviolet radiation has a shorter wavelength than the visible violet light. Infrared radiation has a longer wavelength than visible red light. The white light is a mixture of the colors of the visible spectrum. Black is a total absence of light.

Ya still with me? OK then.

Red light has longer a wavelength and less energy than violet light. This is the reason that the color red is the first color to fade away under water. The color red will eventually fade to black as you get deeper under water and light penetration diminishes. In clear water you can see the color red at much greater depths than in dirty water. Eventually as you go deeper to where light cannot penetrate at all every color of the visible spectrum will fade to black.

Enough of that stuff my brain hurts.
I'll try to answer your questions now

If red 'disappears' underwater, does fish blood disappear underwater also?
> Nope, but only because it coagulates underwater almost immediately.

Can fish see their own blood?
> Only when they are bleeding in shallow water.

Is a red snapper invisible?
> Only to female red snappers unless they have a fat wallet and a cool car.

How come bass didn't adapt to turn red so that they could be invisible?
> Hey, evolution takes a long time. Be patient.

How come no freshwater game fish are red?
> What, Goldfish aren't good enough or red enough for you?

If I wear a red wetsuit, can I hide from sharks?
> Ummm, no.



Hey Lake, I'm watching you }(