12 o'clock
`` Slow to two knots , Williams , '' ordered Frank . Williams signaled the engine room and the pace of the submarine slowed down until the vessel was barely moving through the water . Frank glanced at his watch . It was 12 o'clock . `` Fifteen minutes in which to lay the mines , '' he said to himself . `` They must explode at 12:30 -- '' At 12:10 the submarine emerged from the depth and floated calmly upon the surface of what appeared to be an artificial harbor . Frank and Williams , leaving Jefferson at the wheel and ordering the engines stopped , sprang on deck , carrying two small packages each .