I have speared some fish using the frog gig that was mentioned in one of the posts above. Two observations that are critically important: Fish can accelerate from zero to gone in the blink of an eye -- take that into consideration when you make your move. The other thing; when you look at a fish setting motionless in the water, remember that little thing called "refraction." Due to the bending of the light when it strikes the water, the fish is not where he appears to be. The best aimed shot will be a complete miss, unless you understand this.
If I remember my 8th grade science correctly, the angle of refraction is dependent upon the location of you, the sun, and the fish. Perhaps someone on the site can give a more detailed explanation of this phenomena.