Spear fishing is a blast. Heck, just being in the water is incredible. There's nothing like getting into the ocean and hunting. There is so much involved. Breath hold, aim, range, being completely silent, and blending in with the environment so that the fish hardly notice you are only some of the challenges. There are also tons of tricks for different species of fish to learn and develop. I believe it's illegal in many fresh water locations. In the ocean different things are protected in different locations. Make sure you know what they are.
I still enjoy fly fishing and bait fishing. However, now that I've been in the water to hunt I always wish I could throw on my gear and get in when I'm holding a pole. No contest to me.