Missed the beginning
How is Doc involved with Larry Wilson at the start of the movie?
shareHe was drunk and trying to prove to Larry that he wasn't drunk by walking on the bannister of the ship they were on. Doc fell overboard and Larry got his foot caught on the life preserver and fell in and had his head hit by an oar of the rescue ship causing amnesia.
Since Powell's character sounded the alarm to save him, Doc sat by his bedside until Powell woke up. Then Powell was no longer the man he thought he was, so the two teamed up together.