Whatever happened it seems to have departed the deck after the impact.
"...The aircraft had launched from the USS Bonhomme Richard (LHD 6) and was conducting regularly-scheduled operations when it crashed into the waters on its final approach to the USS Green Bay at 2:07 a.m. ET, NBC News learned.
There were 21 passengers and five crew on board. All went into the water with the aircraft.
Vessels and aircraft from the 31st Marine Expeditionary Unit and the Bonhomme Richard Expeditionary Strike Group immediately responded and were taking part in the rescue operation. Rigid hulled inflatable boats from the USS Green Bay and an MH-60 Seahawk helicopter from the USS Bonhomme Richard began an immediate search. By 3 a.m. ET, 23 marines were recovered safely, including one person with a non-life-threatening injury who was later medevaced to shore for treatment.
The USS Green Bay Flight deck was damaged and left inoperable.
The aircraft involved was described as a MV-22 and was assigned to the Marine Medium Tiltrotor Squadron 265 of the 31st Marine Expeditionary Unit......"