“Ships at sea do feel earthquakes, and if you're directly above an earthquake, they make a lot of noise,” Heaton said. “It's been reported that sailors think they've run aground and usually try to figure out what it is that they've struck, but it's really an earthquake,” Heaton added.

If an earthquake occurs while a cruise ship is in deep water at sea, it is highly unlikely that passengers or crew will feel any vibration at all. This is because the water column acts as a massive dampener; the seismic waves that shake the ground on land are largely absorbed by the water before reaching the surface. Even if the earthquake generates a tsunami, these waves have very long wavelengths and low heights in the open ocean, often passing under the ship as a mere swell that is indistinguishable from standard sea motion. However, the experience is very different if the ship is docked in port. When tied to a pier, the ship becomes part of the "land" structure; the shaking of the dock is transmitted through the mooring lines and the hull, often resulting in a loud "bumping" or "grinding" sensation and physical swaying. Passengers on board a docked ship during a significant quake have reported feeling the vessel roll or bounce against the fenders. In the event of a tsunami warning while docked, standard maritime protocol is for the ship to head to deep water as quickly as possible to avoid the surge that occurs in shallow coastal areas.