Sound carries very efficiently in water. https://oceanexplorer.noaa.gov/explorations/sound01/background/acoustics/acoustics.html https://oceanexplorer.noaa.gov

Sound carries very efficiently in water. https://oceanexplorer.noaa.gov/explorations/sound01/background/acoustics/acoustics.html https://oceanexplorer.noaa.gov/explorations/sound01/backgrou... https://news.cornell.edu/stories/2005/02/secrets-whales-long-distance-songs-are-unveiled https://news.cornell.edu/stories/2005/02/secrets-whales-long... The sub should have had an acoustic transponder that broadcast telemetry which could also be used to locate it.