Would tend to agree with the possibility of an old mine detonating near the ship as it passed, but not actually struck the mine. I say this because they saw a flash, heard an explosion and some sort of pressure wave smashed windows and toppled furniture around. Had it been a rogue wave I would have expected to see more damage along the length of the ship, or at least towards the bow (hitting the wave on an angle rather than broadside or head on) and I don't think it is an impact from a solid object as there is no damage visible to the paint which I would expect to see as it would be next to impossible for the ship to be hit broadside with no sideways motion I would think.