Hello, and welcome to the forum!!

I have an 18 x 36 rectangle, hopper-style pool with 8 1/2 foot deep end, and the water STILL gets very warm for swimming in July and August, unless I run tap water through my slide to cool it, or run my pump at night with a fountain. I'll let one of the engineering-types chime in here, but my personal opinion is that, if the pool is in full sun all day like yours, (and mine!), you're not going to be able to get a deep end deep enough to keep the water cool during the hottest part of the summer.
You might need to just explore other methods of cooling the water.