According to Press TV, US Central Command (CENTCOM) said in a statement on Saturday that the chopper went down during training about 20 miles (32 kilometers) off the southern coast of Yemen at 7 p.m. local time (16:00 GMT) a day earlier.
According the statement, search is underway for a missing US service member who was on board, while the five other service members aboard the helicopter had been rescued.
The Central Command noted that an investigation has been launched to determine the cause of the crash.
“When the incident took place the helicopter was not very high above the water,” CENTCOM Spokesman Colonel John Thomas said.
Yemen has been under regular US drone strikes, with Washington claiming to be targeting al-Qaeda elements, while local sources say civilians have been the main victims of the attacks.
Washington has over the past months stepped up its such air raids after US President Donald Trump in March gave the Central Intelligence Agency (CIA) new powers to launch drone attacks against suspected terrorist targets.
The authority had been limited to the Pentagon under the former US administration.
In January and May, the US conducted deadly ground and aerial raids on Yemen, leaving dozens of people dead in total.
According to a report by Business Insider in mid-August, Trump is expected to break his predecessor Barack Obama’s record of dropping the most bombs in the countries where the US is militarily intervening.
The report said Trump has escalated US military involvement in “non-battlefield settings,” including in Yemen, which has seen 92 such operations.
Washington has been a major supporter of the Saudi regime and its allies in their bloody offensive against Yemen, which was launched in March 2015
The US has been providing huge amounts of arms and military training to kingdom’s military.
The aggression, which seeks to restore Yemen’s former Saudi-allied government to power, has martyred over 12,000 people, according to the latest tallies.
The US-backed Saudi war has fueled the chaos in Yemen, paving the way for al-Qaeda and other terrorists to increase their acts of violence.