There are many ways you can do this. To me, the easiest way is cross multiplying, but since the denominators are the same, there is no need to do that. Also, the fractions are negatives, the one closest to 0 is closer to the surface of the pool -4/5 = -2/5 in this case -2/5 is closer to the surface of the pool.
Answer: the boy's feet are closer to the surface of the pool