To determine the depth of the water, let's use the Pythagorean Theorem.

where c = the length of the hypotenuse and a = length of one of the legs.
Since c = 15 ft and a = 6 ft, let's plug them into the formula above.

Then, solve.


Get the square root of 189 using a calculator.

Therefore, the water is approximately 13.7 feet deep.