If I jump off the top of my rock waterfall and do a cannonball, my bum hits the bottom of the pool. Not hard, mind you, as the water is enough to slow me down, but diving is dangerous in a pool that's not designed for it even if a diving board is not present. The human body can move quite quickly underwater when diving as opposed to simply jumping in. There are minimum design constraints for diving pools (well depth, maximum allowable floor angles, head room, etc) for those very reasons - to protect a diver against head injury.
Best to always have a sign around a pool that states "NO DIVING" and make sure all guests and children are properly instructed. I've pulled my kids out of the pool and have made them sit out on 15min penalties when they disobey the rules. Embarrassed the heck out of my oldest son once when he did something stupid and I pulled him out while his friends got to stay in and play....he hasn't broken a pool rule since.
Mine is 7 to 7.5 feet. Some day the deep end will be the shallow end with a 4" deep lounging area stepping off to 2 feet then getting deeper to 4 and back to 3 at the current shallow end. We just don't need a pool so deep as we mainly just hang out in it with cocktails with the kids being grown up there's no need for all that ruckus anymore! Of course dollar wise this is in the long term not the near term.