This is the forefoot of the rudder. I was going to glass in that bottom piece of oak, and round and glass the end grain on the leading edge below the bottom pintle. I accidentally sat on the rudder when it wasn't flat. I'm glad it happened now and not at sea!
Water got in. Glue not waterproof. Wood rotting.
Water entry could have been from the prop damage, or could have been from a break in the epoxy in the end-grain on the edge of the rudder, which didn't have glass over it.