We "found a submerged rock"....the hard way, back in 1974, onboard HMCS PORTE QUEBEC, in Barkley Sound, on the west coast of Vancouver Island, Canada. We came close to loosing the ship. We shored-up badly leaking deck hatches, got the flooding under control,, and brought the ship back into safe waters. First (and only) time I did shoring for real. We put an 11' gash in the hull below the waterline, sprung the stern gland, and sheared 18" off the propeller. The first point-of-contact with the rock was right next to my bunk - luckily the hull was penetrated there, or the Mess Deck would have flooded, and we would likely have lost the ship (and me).
Chris, in Victoria, BC