First, calculate the pressure at which the window can be exposed, from the force it can withstand and the area. Second, calculate the depth of the sea for the calcualated pressure.
I will assume that the diameter of the window is given in cm and that the force is given in newtons.
1) P = F / A
A = π*r^2 = π(0.20 m)^2 = 0.125664 m^2
P = 1.20 * 10^6 N / 0.125664 m^2 = 9.549*10^6 Pa
2) Conversion: 1 meter of seawater = 10069.3064 Pa
9.549*10^6 Pa * 1 msw / 10069.3064 Pa = 948 msw
Answer: 948 m under the sea
