Gary Giordano is revealing new details about the events surrounding the mysterious disappearance of his travel companion, Robyn Gardner, who vanished while the couple were on vacation together in Aruba.

The two were snorkeling, according to Giardano, when Robyn was swept out to sea never to be seen again, something Aruban officials don't believe, claiming instead that the young woman is dead.

Giordano told Dateline in a televised interview that will air Friday on NBC, that he realized the two were getting in deeper water during their “snorkeling trip” and he tried to signal to Gardner to return to shore.