Let's find the length of the side of the pool.
Let it be x, so the diagram is:
Using the pythagorean theorem, we can figure out x. Shown below:
So, 30 meters is the side length of the square (pool).
The area of a square is:
Where "s" is the side length
We found s to be 30, thus the area of the pool is:
Thus,
Ulysses is correct.