Stewart disappeared after surfacing on Tuesday evening (31 January) at Alligator Reef, six miles off the Florida Keys near Islamadora.

He had been rebreather-diving on the 70m-deep wreck The Queen of Nassau, and it has now emerged that it was his third dive of the day. Divernet reported on his disappearance the following day.

Stewart’s buddy is reported to have lost consciousness after being taken aboard the dive-boat, and while he was being recovered Stewart, who had surfaced and given an OK sign, vanished from view.

Weather conditions have remained good in the area. The US Coastguard, US Navy, Florida Fish & Wildlife Conservation Commission, Monroe County Sheriff’s Office, Sea Shepherd and Key Largo Volunteer Fire Department have all been assisting with the search efforts by boat, aircraft, helicopter and diving.

Coast Guard officials have stated that there is no set time when the search would be called off.

Stewart, best known for his award-winning conservationist documentary "Sharkwater", was diving in the area as part of work on a sequel called "Sharkwater: Extinction".

The online appeal site can be found here

The organisers say that any excess funds will be donated to FinFree, a campaign to combat shark-finning worldwide.

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