how does montgomery feel about saving prendick's life

Prendick and Montgomery, after dinner with the ship's mate (the captain having passed out on his cabin floor), go onto the deck rail to talk. Montgomery seems painfully reminiscent of London, and Prendick tries to satisfy him with as much news and gossip as he can remember. Prendick thanks him for saving his life, and Montgomery verges on revealing his past, alluding to how he "lost [his] head for ten minutes on a foggy night." Montgomery is obviously unnerved about this memory and having Prendick on the boat but I think saving him is something Montgomery had to do. But Montgomery eventually decides not to share his story, and Prendick does not pursue the matter.