Well your still going to be wearing a weight belt, bcd, fins,a mask and a respirator so there's a limit to how nude you can be. Oh and the water gets pretty cold sometimes...;-)

You just gotta watch out for the crabs.

Same as in a wet suit only there is more shrinkage :P

Heh! Good one! Seriously, there ARE some important things to consider: Water temperature. One would think that diving in warm water (80 + degree F water) would be OK. but it's really not, for very long at a time. Your normal body temperature is nearly 99 degrees F, and cooler water surrounding your body acts like a heat sink...and cools you down. If you aren't wearing at least farmer-johns, in a short while (even an hour or so) the water could have you shivering violently. Your body will start shivering when your core temperature reaches about 95 degrees or so. Another one is practical considerations with respect to the equipment you carry. Wearing a weight belt and fins may cause chafing if you don't have at least some protection between you and the equipment. And your surrounding environment is important as well. Rocks, barnacles, shells, and coral (coral expecially) may have sharp edges which will cut like razers, if you aren't Careful. Diving where you may come into contact with such can be dangerous. Especially if you have strong currents to worry about. But as long as you take all that into consideration, you should have no problems!

Considering those tiny evil jellyfish you Australians have swimming around your continent, I wouldn't suggest it.