Curufin didn't think Gladio had anything to apologize for. They all did what they could do.

"You have a point there. We're just sitting here in the middle of the ocean, and we already know there are monsters in it. So, the train is a sitting duck! It's well that somebody is staying behind to protect the others who are staying behind. Not to mention the Voidtrecker Express itself. We can't afford to lose our transportation, if it should happen that a really large, really fierce monster surfaces and perceives the train as a rival or as a meal."