This is a really impressive, detailed and insightful discussion of the sinking of a singlehanded yacht by its skipper and naval experts involved in the refit of the boat. Their consensus seems to be that only a large breach of the main compartment (the salon) and not the other watertight bulkheads would have swamped the boat in such a short time. So possibly hitting a submerged object like a shipping container at just the right angle was the cause.