Negative numbers don't have real square roots since a square is either positive or 0. The square roots of numbers that are not a perfect square are members of the irrational numbers. This means that they can't be written as the quotient of two integers. So you have to use the "imaginary number", i.
Ana is 35 meters below the water's surface, so if Jesse is 8 meters below her, you would add 8 to 35 and end up with 43 meters below the surface of the water.
