This is the Underwater Explosion Test Pond used for testing full scale underwater structures (submarines?).
Further to the ESE is the much smaller Briar Point Test Pond used for UDEX testing of surface models.
Picture of Briar Point Test Pond
http://www.dt.navy.mil/sites/uerd/briarpoint.html
Scientific - Test Facility
Links: www.atc.army.mil
By: kjfitz