Depth Of Water
The water deepness is the water depth. You should check this before diving into the water so you don't hit your face.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
I've dived to depths of one hundred feet before.
You don't have to worry because this pool is very shallow.
While diving at a depth of ten meters, I found rainbow-colored seaweed.