I suspect this are really in there to make legal the lights that already exist in some spas and pools with a "sun shelf" (a 6 to 10 inch deep area). The light John is talking about to illuminate the deep end will usually be in the side wall. I still say you are not getting a pool light out of the niche without getting wet. All the code is saying is you need enough cord to be sitting on the deck when you take the thing apart.
