Did you waterproof your battery? Have you tested the light? If you can come up with an adapter you can connect the light directly to the charger or any other 6-8V power supply to test it. If the light works then it's the battery. It's a known issue, the battery is not waterproof and there is small circuit inside, when it gets water inside the circuit board dies either gradually or instantly. The circuit can be replaced for under $10 shipped.
Adam