Our's didn't sink because we were just one mile away, it took about an hour to tow it to shore.

From memory the crack is 5 to 10 inches forward of the main beam. I never saw the inside of a Supercat, didn't look inside the crack and don't know if the SC15 has a bulkhead. Do you know where it is supposed to be?

When I find time to tow the boat to the shipyard, I'll bring a lantern and camera to search for the bulkhead and take the necessary pictures. Yesterday I only had time to disassemble the boat for transport before it was dark, no time to take pictures, even if I had a camera with me.