[jmk]

To answer your question, yes, in a heavy rain water can come in through your deck hatches. I've seen this happen and it occurs when the drain channel overfills. But there is no reason for guesswork here. Do as Capt George has suggested to many others: dry your bilge, then spread talc powder anywhere a leak could occur. Harmless and easy to wash away, talc will show the leak. I had one coming in through the base of my radar arch! Drove me nuts.