[Sebastian knows how ridiculous all of this sounds, and if he hadn't already been through several of these portals himself, he wouldn't believe himself either.
However, so far he did neither encounter sea monsters, nor did he die in these scenarios, and fake as they might seem, he is not sure how death or injuries would translate to his body outside of these experiences.
And he doesn't want to find out now.

He is still clinging to the mast, with the stranger in his arm, both of them holding on to the only piece of wood that's still above water, but constantly getting closer to the water's surface, and he can already see the sea monsters lurking, teeth and claws at the ready to grab at them.

The other's call makes him turn his head however, trying to spot what the other has seen.
And indeed, it looks like a patch of several bubbles, all collecting there, ready to be used to escape the chaos.]

Yes!
Good! God, damnit.
Think you can jump and either swim fast enough or manage to get to one of those boxes and to the bubbles from there?

[because he isn't leaving before he knows that the stranger is safe]