Defense Minister Kim Tae-young has said that a floating mine dispatched from North Korea was one possible explanation for the blast.
From the stltoday.com
A floating mine, which is nonsense.
From the time.com
A Harvey Torpedo was a type of floating mine towed alongside a ship, and was briefly in service in the Royal Navy in the 1870s.
From the en.wikipedia.org
South Korean officials have said they will examine all possibilities, including that the ship might have been hit by a floating mine or a torpedo from North Korea.
From the chron.com
It is considered still possible that the Cheonan was sunk by an old mine floating around in the seas where it went down.
From the post-gazette.com
Currently, MSHA relies on lab tests that take a week or more to determine how much airborne rock and coal dust is floating around a mine.
From the sltrib.com
A contact mine is one of those that had an anchor and a cable, and a mine is floating just below the surface with all these little horns on it.
From the courier-journal.com
This process can be carried-out from land surface, open pit floor, underground mine or floating platform or vessel through pre-drilled boreholes.
From the en.wikipedia.org
It's one of mine, anyway, that I happily daydream about while floating over the slopes on a chairlift.