There are two different ways an oval pool deep end can work for you. One end of the pool can be deep while the other end is left shallow, or standard depth. The other way is to have as much of the pool area as possible at the deeper level.
An oval pool with one end deeper can be used in a couple different ways. It can be a place to jump into off of a wood pool deck. Although this is frowned upon in all the safety manuals we all know that kids love to jump into pools. A deep area at one end of the pool provides a safe place for jumping.
Digging the majority of the pool area out to a deeper, but still level, area is an option used by many people. Volley ball is a popular game in oval pools, having the playing field the same on both sides of the net is helpful. If it is mostly adults, or older teens, that will be playing the game a little extra depth could make everyone more comfortable.
Oval pool deep ends can be dug to any depth that will best suit your needs. You can dig an extra 30" at one end for the kids to jump into or you can dig an extra 8", across the majority of the pool, for the adults.
Before digging your oval pool deep end it is strongly recommended that you have all of your side buttresses set and the end rails laid out and leveled. This may seem like an obvious point to make but it truly is important. Almost every time I go to do an install where the customer says the deep end is already dug it is way too big. A deep end that is dug too big needs to be backfilled, packed, watered and packed some more. You can not just throw some dirt back into the hole and set the pool up. The ground will compress under the weight of all the water and loose it's shape. If the backfilled area goes into the buttress area, as it usually does, the integrity of your pool is greatly compromised. That is, until the ground has been put back and packed solid.
I place my foot at the end of the buttress assembly and put my shovel just past my toe. That is the start of my deep end. A gradual slope is then used to reach a point somewhere near the center of the pool. Depending on the size of your pool, the bottom of the hole may only be 2' across. On a 12' wide pool, allowing for the buttresses and the slope, the deepest part of the pool will be less than 2' across. This is still plenty enough room to jump into, or for several people to stand up in. The length of the deep end will be much more than the width, and that again depends on the size of the pool and how you choose to dig it.
The starting point for the sides of your deep end is dictated by your side buttresses. The ledge at the deep end of the pool is dictated by the pool bottom rail. The bottom rail must sit on a firm, level ledge. This ledge will hold the bottom rail and the pool cove. It should them be big enough to flatten out beyond the cove before the slope begins. I have seen this done with as little as a 1' ledge but I much prefer 1' 6" to 2'. When the hole is done the sidewall is going to have to be installed. Having a ledge to walk on, and roll the sidewall on, becomes very important. It is no fun to fall into the deep area with a new sidewall falling on top of you. The new sidewall does not look so new anymore, and you would rather be building a pool than visiting a hospital.
The slope coming out of the deep area and into the shallow area is the one you have total control over. This is where the deep end will change to a more gradual slope. You can choose how gradual to make the slope and also how much shallow end you want. A normal oval pool deep end would leave about 1/3 of the pool at the shallow level.
Instructions and advice for installing a liner into your oval pool deep end can be found on this page.