Tricky(?) Crocodile Maths Exam Question

[peacecalc]

Hello all,

it is another version of the problem, which I call the "lifeguard" problem. In reality the lifeguard takes the shortest way through the water (and the longest way over the beach), because that is faster as he tries to find the best (fastest) way with mathematics (the drowning man/woman will be gone to water).

It is the mechanical analogy of snell's law in optics, both have the same solution.