Contractor rec's for swimming pool leak fix (leaking through pool light)

If there is a discrete leak, and you know where it is, you can seal it yourself using underwater sealant. I can't refer you to a specific brand because I won't do the product research until my light leaks. All I can say is that fixing leaks can be expensive if your solution is to throw money at it. But if you know where the leak is and you can access the spot without destruction, 90% of the trouble is already solved.