wait, aren't they on a school-ship? If that's so...how come they can feel an earthquake on a big ship, on the ocean/sea/water? Unless it's a seaquake :0

(Speaking of seaquake...i remember seeing a manga/doujin, whatever it was...about one of those schoolships sinking..i think it was the oarai ship...if anyone knows what i'm saying i'd like to know it)