The main purpose of dry docking was to remove the propeller and tail shaft and associated bearing to ascertain their condition. But it also gave us the opportunity to inspect the hull after all the marine growth was removed.We used a ultrasonic tester to guage the thickness of the plates. We were also able to remove a fishing bouy that jammed in the bilg keel on our way back from the IFOS two years previously. At the time it caused us great concern as is banged against the hull. We had no idea what it was.