Hatches, Rub rail, rail stanchions, cleats. Anywhere there is a hole in your boat, the water will EVENTUALLY find its way in. Its easiests to trace in a hard rain. If you have someone use a garden hose, expect to need to shoot it at different angles for a long time. It takes a long, long time for water to wick its way in and a slow drip can take hours to reach the furthest point. Find the lowest furtherst point of a wet spot and start tracking it uphil. Water will tavel horizontally as a drip along an edge or a cable.