+1 on the taste test for boats living in salt water. Best method ever for finding deck leaks is to use a pressurised common garden sprayer and hit all the suspect looking areas on the deck one at a time from different angles. Don't be surprised when a found leak exits the boat at a totally different location to the source.
That _seems_ like it should work.
However, I have a leak around my mast somewhere (big surprise, I know) that I can't reproduce with a hose no matter how much water I spray at any angle. Yet a strong storm will bring drips or even a tiny stream every time.
Obviously, there's _some_ angle that I haven't tried. I just can't figure out what it is. The mast is coming off this winter, so I'm going to pull off the crown plate and visually inspect everything.
I know ... no boat is 100% dry, but this one is SO close! This is the only leak I have left as far as I can tell, so I'm determined to stop it!