I can understand if the light go out as a result of a faulty string, broken bulbs, ect. but at what point do you put the responsibility on the customer to check this stuff. Ie Customer calls, my lights are not working. you respond No problem I'll come take a look, but there will be a service charge is its something simple like a tripped GFI/breaker.
FWIW I do a lot of RC boating. and water and electronics really don't mix. but I use a Chemical called corrosion X, I have been able to run servos, receivers, batteries under water with no loss of connection or shorts..
I've also been using Fluid film on new applications and getting good results.
might be something worth looking into..