Idea for finding leaks

[Cheechako]

I had a boat that would leak somewhere under the headliner on occasion. While living aboard in Florida, I decided to remove the entire headliner and just wait and watch. In FL about 3 days a week it would literally downpour so bad you couldnt see more than 100 ft outside. Usually with thunder and lightening. So I waited... and waited. No leaks visible. A week later I put the headliner back. Next storm... yep there's that drip!
Eventually I "fixed" it with "Captain xxx? Creeping Crack Cure". A white liquid latex like stuff. My wife actually picked it up. I probably would have never bought it. You go outside and put it around anything suspect and it wicks inside, sealing it. Kinda of a horshit cure for sure. Surprisingly.....My leak was stopped. Go figure. I applied it to deck turning blocks and handrail bases on the cabin top.

[Miz Pea]

This Capt. Tolleys is interesting stuff. Has 10 or so good reviews and one bad review. Read about it here:

https://www.westmarine.com/buy/capta...ealant--243990

[oleman]

On a USN fighting ship with watertight integrity, a compartment is pressurized to 5-10 PSI and we would a bubble test. We had a high volume low pressure air source and of course an AP regulator because it would be possible to expand something! The hull was also x-rayed, a process known as gamma graphing for problems that did not show.
Our old work boat is mostly leaks so pressurizing is impossible! We look for leaks with a flash light after dark.

[nhschneider]

When we have leaks that are hard to find, we use a shop vac to pressurize the interior, after sealing everything up tight, then soaping the decks down well. We call it giving the boat a 'blow job'. However, we've tried using household fans and even commercial carpet drying fans with poor results. Our experience is that it takes a high output, commercial shop vac to work.

Fair winds and calm seas.

[LooseGoose]

You might add a bit of food coloring dye to each dam, perhaps of differing colors.......