First we apply Snell’s law and solve for the angle of incident Θ.
Incident angle i = Θ and refractive angle r = 45°.
Refractive index n1 in water is 1.33 and refractive index n2 in air is one.
Incident angle is 32.1°.
From the geometry of the diagram, we see that
d = 2.71 m
Pool true depth is 2.71 meters.