1. The problem statement, all variables and given/known data refractive index = 1.33 (water) real depth = 10m 2. Relevant equations refractive index = real depth divided by apparent depth 3. The attempt at a solution I'm going to call apparent depth X 1.33 = 10/x So I multiply 10/x by 10 so that i have x and 1.33 x 10 is 13.3... that's right, isn't it? but that makes no sense, because the apparent depth must be less than the actual depth. I know the real answer is 7.52.. what am I doing wrong? No idea if the problem is with my maths or my physics.