I read that to find the depth of the water in CAW is to place a fish spawner on the water and then check the coordinates. Info is in this post - https://forums.thesims.com/en_US/discussion/810760/dive-lots-and-water-levels
I've never had any dive lots in any of the worlds I use as the depth seems to be too shallow and they stick up out of the water. I've also read that water depth doesn't matter as there is no mention of water depth here - https://www.wikihow.com/Move-and-Place-Dive-Spots-in-Other-Worlds-in-Sims-3:-Island-Paradise
Anyway, I hope someone sees this and has some better advice then what I can give as I'd like to have dive lots in my shallow water worlds ; )