I found water in my perko nav lights also. Pulled them & found the rubber seals were dried out & cracked. I had a tube of "Big Stretch" made by Sashco & purchased at Ace hardware that I use around the house for many sealing jobs. I wiped down the cracked seals with lacquer thinner & laid a thin bead of big stretch on top of them, let them dry a few days until fully cured reinstalled them. Problem solved cheaply! Vern