Water is sprayed onto the pool surface, creating a ripple effect, so the diver can see the surface. Without it, the water takes on a glass-like appearance, and all you can see is the bottom of the pool. The diver needs to be able to spot the water surface in order to enter the water correctly in the vertical position.
Water fountains circulate water using a water pump. Water is pumped out of a low pool of water, up through the inside of the fountain, where it then falls back into the pool of water. A simple fountain might have a single spray of water pointed upward, whereas more complex fountains can have many spray heads pointed in different directions creating designs and effects. The water is under pressure from the pump pushing it through tubes.
I have seen many pools with spray nozzles that spray return water as a mist over the surface of the pool. If the circulation pump is turned on at night when the outside air temp drops, the misted water releases some of its heat into the atmosphere, and it falls into the pool at a cooler temp. The best way to cool your water in the summer is to buy fountains that plug into the outlets that carry water from the pump. Besides being famous for cooling the water, they are pretty.
You can kill them with a spray bottle of skin-so-soft oil and water mixter spray all around the sides of the pool and put son directly on the water. It makes the pool smell good and doesn't hurt anyone or anything! Oh and your skin is so soft after swimming! I knocked em down in an hour and killed them completely off in a couple days!