Dave Morton of Ocean Acoustical Services and
Instrumentation Systems, Inc., throws a sonobuoy hydrophone receiver over the side of the research vessel Endeavor during the Autonomous Wide Aperture for Cluster
Surveillance (AWACS) project in 2006. The sonobuoy measures the propagation of sound in the sea and transmits the data back to the ship through a radio link.
(Photo by Craig Marquette, Woods Hole Oceanographic Institution)