i built a sports pool (shallow pool) and had dreams of wonderful volley ball games. I anticipated that with 8 adults/teenagers we could play 4 v 4 on a regular basis with friends. My pool is 18'x40', the shallow end is 3' deep, the middle area under net is flat and 3.5' deep, the deep end is 4'. my dreams turned out not to be true. It is surprising how little most folks can move in 3.5-4' of water. The only time we've had a successful volleyball game was with 16 adults/teenagers. Kid's generally 10 years and younger either don't have the arm strength, coordination or experience to hit a ball to any particular spot while in the pool. I've tried all types of balls, the most successful being the ones about the size of a basketball but light weight plastic (small beach ball). Our pool is vinyl so while that is good on the feet you have little traction. I'm 6'1" and can cover about a ~8'x8' area of the 4' deep part of the pool. That would mean I would need 6 of me to cover 1/2 the pool. In 3' I can cover more area and we could cover 1/2 the pool with only 4.
If I could do over I would ditch the volleyball idea and have put in a real deep end for shallow diving. I and the kids dive in the 4' deep area but we don't let guests do it. I've also had several dads just randomly jump in the pool at parties and do a cannonball (thank god) and they impact the bottom fairly significantly. If you do want to have a net i'm extremely happy with mine, I have stainless steel pipe inserted into the pool deck with SS covers for when the net is not actually put up. The net uses SS pipe with a top cap. The ropes supporting the net are Kevlar and I can tighten the net such that I can hang on it with one hand and it only pulls down a few inches. important because kids will be climbing pulling up on it when you aren't lookin' even after you tell them not too LOL.