Rob Stewart, a Toronto filmmaker best known for his award-winning documentary Sharkwater, has gone missing while diving off the coast of Islamorada in the Florida Keys. 

According to media reports, Stewart came up from his dive and was ready to be picked up, then disappeared under the water for a second time not to return to the surface. There is no word yet on why this happened, and the Coast Guard was set to begin a search at sunrise this morning. 

The Coast Guard released information stating that Stewart had gone missing near Alligator Reef at 5:13 p.m. on Jan. 31. 

"Coast Guard watch standers issued an Urgent Marine Information Broadcast, launched a Station Islamorada 33-foot Law Enforcement Special Purpose Craft boat crew, launched an Air Station Miami MH-65 Dolphin helicopter crew and diverted the crew of the Coast Guard Cutter Charles Sexton."

At 6:46 a.m., the Coast Guard Twitter account @USCGSoutheast said the search was continuing. 

An update from someone identified as Rob's Sister Alexandra Stewart called attention to the need for a "small, low flying/slow airplane (preferable) or a helicopter to search this afternoon from about 2pm-4:45pm or as late as 6:15pm. Would be even better if it came with experienced searchers. Please call 416-805-0100 or Tyler 424-212-9995 in the Florida Keys."

Stewart's Instagram account is filled with thoughts and prayers from hundreds of concerned fans. 

Following the success of Sharkwater in 2006 after it won some 36 awards, Stewart spoke to Post City about his second film with an environmental focus — Revolution. Recently, he has been filming the second installment of Sharkwater.

Stewart grew up in the Bayview and York Mills neighbourhood and learned to swim at the Douglas Snow Aquatic Centre. He earned a degree in marine biology at the University of Western Ontario (now Western University). He started filming Sharkwater when he was just 22 years old.