Scientists at the NOAA EarthOcean Interactions (EOI) Program at Pacific Marine Environmental Laboratory (PMEL) and Oregon State University heard the March 11, 2011 Honshu, Japan earthquake using a hydrophone located near the Aleutian Islands of Alaska. The normal low frequency of the earthquake sound in the water would not be audible to a human swimmer. On this video, the earthquake sound has been sped up so that it plays back at a higher frequency which we can hear.
For information on the underwater microphones, see https://www.pmel.noaa.gov/eoi
For tsunami information, see https://nctr.pmel.noaa.gov/honshu2011...