The door was locked and I was informed that to save the captain I need to get the key to the bridge from the crewman. How do I get it? Where do I find this crewman?

This part of the game is sooooo misleading - after hours of searching the boat for the "crewman with the key" I found out that you'll get the key right after you use the lift to send down the fixed pipe. Activate the lift again to bring it back up and open the hatch - the key will be sitting right there.