Could you be referring to the wreck and sinking of the Alaska Steamship line ship the Yukon?. It sunk after hitting a reef south of Seward in 1944. All but six people survived. The six that did not survive were soldiers that were on a different part of the ship. I have been told by my mother that the Yukon split in half width-wise. My mother was going to be on the ship but decided to wait for the next steamship that was sailing out. My brother said that the Yukon hit a "black reef(?), probably a reef that could not be seen.