Rob Stewart disappeared under the water near a shipwreck as he was filming the follow-up to his award-winning new documentary Sharkwater: Extinction.

Officials for the U.S. Coast Guard have confirmed a search is underway for the 37-year-old, who was last seen on Tuesday evening (31Jan17).

His sister Alexandra Stewart told reporters on Wednesday (01Feb17), "He had surfaced and gave the OK sign and then he was gone."

Stewart's family members, who are helping to manage the search party, have set up a GoFundMe page to cover costs if their efforts are extended.