Human Torpedo?

Now this is interesting:

Kim said a torpedo was not detected by the Cheonan but said in response to a lawmaker's question that a "human torpedo attack" was also one of the possibilities.

A local newspaper report said North Korea has two-manned torpedoes, citing "former North Korean navy men who defected" to the South.

The two-manned submarines are fitted with two torpedoes or a mine and move underwater at a pace slower than two kilometers per hour to avoid detection.

Shades of the Decima Flottiglia MAS. I don't see, however, how the human torpedo could have approached and attacked Cheonan, unless the latter was essentially stationary.
H/t jhpigott.