FYI
Someone posted a link to a video on this stuff a while ago, it showed a leaking glass being sealed whilst the water was still running. Impressive stuff on film.
Bought a tube to try & left it on the van.
Got a call this morning from the bloke who owns the local burger van, water pouring through the ceiling of the trailer around the skylight, council health inspector had just arrived for his regular check!
It was chucking it down here this morning, really hissing it down.
Removed the screws & frame from inside & then removed the skylight from the roof. Must have been 1/2" of standing water on the roof, no drainage channels I could see. Couldn't get rid of the water, even tried tilting the trailer using the jockey wheel.
I applied a thick bead of this stuff around the skylight flange, pushed it into place, leak stopped immediately, refitted the inner frame, not a drop of water anywhere.
Watched it for 20 mins while I ate my free bacon roll, called them later to check, not a single drip.
So, it does work on wet surfaces and even underwater. Bloody incredible stuff.