After a good rolling session, I can count on 1/2 inch or so of water in the rear compartment of my precious rotomolded boat. I suspect it's from the multiple piercing from the rudder, cables, deck bungees, togs, etc. and not the neoprene hatch cover itself or foam bulkhead.
I suppose I could fill it with water, tilt it this way and that, and look for the wet spot. Something I'm not looking forward to in this cold weather. Are there better ways? Enquiring minds need to know.