How can a jet disappear? In the ocean, it's not hard

Sea Hawk helicopter
In this handout provided by the U.S. Navy, a U.S. Navy MH-60R Sea Hawk helicopter from Helicopter Maritime Strike Squadron (HSM) 78, Det 2, assigned to the guided-missile Destroyer USS Pinckney (DDG 91), lands aboard Pinckney during a crew swap before returning on task in the search and rescue for the missing Malaysian airlines flight MH370 on March 9, 2014 at sea in the Gulf of Thailand.
Senior Chief Petty Officer Chris D. Boardman/U.S. Navy via Getty Images