This is a problem indeed.

My frst suggestion/observation is that these watches are really not meant to be used in the water. Silverstones may be better than some (Monacos for instance) but they were never that waterproof originally, let alone now. You could speak to someone like Nic at Heuerboy.com, he may have suggestions, but i doubt many (if any) on this forum use their vintage Heuers in the sea, shower etc.

Condensation is something that i had a problem with on a Autavia in the summer. In an ideal world you would get the back case off and let the watch dry off naturally in a neither hot nor cold enviroment. best advice is to not panic, i found mine naturally sorted itself in a day or two, but i wouldn't wear it again until this sorts itself out.

I'm sure some of the more "hands on" guys will post further ideas, if in doubt give Nic or Abel a shout and i'm sure they will advise more thoroughly...

Cheers

Rich