When you stand by the side of a pool someone swimming underwater appears to be in a different location than she really is the effect is called what

Deep shallow because when you in the pool and it look like you there but you really not that mean deep shallow when you see yourself then that mean shallow cause you in the pool and it appeared to  be your shadow so its called shallow

Apparent depth

Where
n= real depth / apparent depth

Apparent depth is the depth which we think the person inside the pool is...