The former chief engineer of a container ship that sank in a hurricane killing 33 sailors said evidence from the ship's "black box" shows a crew working hard to keep it afloat.

Mark Gay, who served aboard the El Faro years before its final journey, became emotional at times during testimony Wednesday before a U.S. Coast Guard investigative board as he talked about the ship's lost crew.

The El Faro sank Oct. 1, 2015, after losing propulsion in a hurricane while traveling between Jacksonville and San Juan, Puerto Rico.

Crews recovered the ship's voyage data recorder, which recorded audio of conversations as the ship's engines stopped and water flooded its interior.

Gay said he read the transcript and believes the crew tried everything they could to save the ship.