I would check other possible sources, like deck hardware, maybe one of the stanchions is leaking for example, which would be a much easier to fix. The problem is the water could have travelled from a distance, maybe stuffing some paper towels all along the entire length of the wiring bundle would help pinpoint the leak, use dark coloured ones so you can see if they are wet. Also double check any post factory installations of hardware. You'll also have to use some fresh water to rinse the salt off otherwise is will just get damp whenever the humidity is up and will look like a leak.
PS31#111 Cielo Azul