For clarification:
Jack, Kate, Sawyer and The Others are camping out in and around the Hydra (the animal research station). This station is on a different island to the one on which the plane crashed. The second island also has its own medical facility. (Of course I may be wrong on these details)
When Jack is taken to try and save the woman who had been shot, a bag is put over his head and he is walked to the operating theatre. The bag and the siren are used presumably so that he doesn't see Kate and Sawyer since he is walked right past them.
So given all this I was wondering why you thought the others needed a boat or tunnel to move Jack.