Jack decides not to leave the island, jumps off the boat

As The Elizabeth is sailing towards Hydra Island, Jack sits alone at the bow while every one else is in the stern. Frank approaches Sawyer who is at the wheel at asks what the plan is. Sawyer says they're going to get "cuddly" with Widmore until they get on the sub and then point a gun in someone's face until they agree to take them home. Frank says that he likes that plan, then goes with Sun, Hurley and Claire down to the galley to find some food.

Sawyer then goes to talk to Jack, giving Kate control of the boat. Jack tells Sawyer that it doesn't feel right leaving the island because he remembers how it felt the first time he left, like a part of him was missing. He says that if that thing pretending to be Locke wants them to leave so badly, maybe it is afraid of what would happen if they stayed.

Sawyer then orders Jack to get off of his boat. He says that he can either keep the crazy talk to himself or go in the water. Jack says that the island is not done with them and a part of Sawyer knows that leaving is a mistake. Sawyer says that he's done with the island and if Jack wants to take a leap of faith, then get off of the boat.

Jack apologizes for getting Juliet killed, then looks back at Kate and jumps into the water. Kate screams for Jack and Sawyer tells her that Jack changed his mind. Kate wants to go back for him, but Sawyer says they are done going back.

So it's interesting to see Jack's transition to being completely a man of faith. He now seems to have complete faith in the island and Jacob's plan, but it's still unknown what exactly that plan is.