For what it's worth, I had water intrusion in my starboard locker on my M-15 IOTA when I first got her.  Underneath, at the forward most bulkhead under the bunk there was one, itty-bitty blister looking ding in the hull and it was passing liquid right at the bulkhead.  Grind, dry, patch, sand, fill, sand some more, a alittle gel coat, sand some more, wet sand, polish and it came out good as new!  Good luck.