The US military said that the incident took place at about 7pm local time.
“US forces in the region are conducting an ongoing search for one US service member who was aboard the aircraft,” the US Central Command said in a statement. “Five US service members who were also aboard the aircraft were rescued by US forces following the crash.
“An investigation will be initiated.”
CENTCOM spokesman Col John Thomas told Reuters that the “helicopter was not very high above the water” when the incident took place.