[reef_guru]

just because there are three pronged outlets doesnt mean its grounded. the extension cords/timer maybe faulty, could try to connect the lights directly to the outlet to elimate that question. at the outlet pull the plate to see if a copper wire is wound with other copper wires or if the copper wire goes to the plugs themselves. and if its a dual plate outlet there should be a jumper from one plug to the other for ground, hot and return. in your circuit breaker box the copper wire and the white wire go to the ground buss. they both do the same function, its added protection. dont stick two hands in the circuit breaker box at one time, use only one hand. if all is good and you know its your lights then you have to go fishing in the light fixture (pun intended). saltwater corrodes everything. more than likely the ground will be a green wire, black is hot, white is return. if anyone of those is corroded/broken then you found the problem. sounds like alot but it really isnt. while your in the light fixture you might want to solder all your connections instead of twist end caps and cover with heat shrink. again, dont stick two hands in the circuit breaker box at one time, use only one hand.