Aboard the USS Curtis Wilbur, April 3, 2010: Crew members of the USS Curtis Wilbur wait for the arrival of a helicopter. The Curtis Wilbur is one of four U.S. ships standing by to assist in a rescue efforts to get to 46 South Korean sailors missing after the South Korean ship Cheonan sank on March 26. Most of the South Korean and U.S. ships at the wreckage site are also there as a deterrent to nearby North Korea, according to the U.S. Navy officer in charge of the American forces there.