At the start of the episode, when the voice says, "Previously, on
Lost," they show the explosion from a different angle. The flash occurs at the end of the dock. The submarine is no longer moored along the left side of the dock.
Then, in the preview for next week, you see some of the Others standing atop a submarine's conning tower.
I think Locke submerged the sub and gave Ben a way out concerning Jack and Juliet's departure. He "outgamed" Ben by thinking up a way to remove the sub from play without destroying it like Ben obviously wanted him to do.
This makes me wonder if Locke's switching sides (joining the Others) might be another game strategy move. He "joins" to gather more information on the Others and to undermine them from within.
That would be very, very clever. Almost Ben-like, in fact.
