Faced with footage of a shark silently swimming underwater, you might immediately hear the Jaws theme song in your head, but many people today also react with respect because of filmmaker Rob Stewart's activism and acclaimed documentary Sharkwater.

"We all know sharks have a bit of a bad rep in history and he did a great job of just bringing awareness and creating a different relationship between us and sharks," said Peter Mikhail, owner of the Toronto Scuba Centre.

Family, friends and fans of the popular Toronto filmmaker, photographer and conservationist are anxiously awaiting news of his wellbeing after he went missing Tuesday following a dive in the Florida Keys. The U.S. Coast Guard is on the scene conducting the search for the 37-year-old Stewart, who had been at work shooting his latest film Sharkwater: Extinction.

Sharkwater, Stewart's award-winning 2007 exposé on global shark-hunting and its negative effect on oceans, has won more than 40 awards at film festivals around the globe since its debut at the Toronto International Film Festival.

It helped people become interested in sharks and their importance to the world's ecosystem, said Mikhail, who helped Stewart promote Sharkwater.

"He created a great momentum for sharks worldwide."

Stewart's overall body of work — which also includes vibrant wildlife photography, the books Sharkwater: An Odyssey to Save the Planet and Save the Humans, as well as the hit 2013 conservation documentary Revolution — has resonated with audiences around the globe and helped ramp up a global shark conservation movement.

"His work with sharks is pretty unparalleled," veteran wildlife filmmaker Jeff Turner told CBC News on Wednesday.

Stewart's oeuvre is compelling because it is obvious he spends a lot of time with and is extremely knowledgeable about his subjects — a critical element of this type of filmmaking, Turner explained.

Toronto filmmaker Rob Stewart went missing during a dive off of Florida Tuesday afternoon. He had been at work on his latest film, Sharkwater: Extinction. (Richard Sibbald/Sharkwater Productions)

"There's a certain element of risk associated with creatures that are bigger than you and can hurt you. But at the same time, my experience — certainly with bears — is that they're far less unpredictable than people think. Just a little bit of understanding and it's very easy to keep yourself safe. I think probably Rob found the same thing with sharks: once you get to know them and you observe them and watch them carefully, you really mitigate this to a large degree. They're not as dangerous as people think they are."

However, it's another aspect of wildlife filmmaking that can prove the most dangerous: the environment itself. Underwater shoots can be "a type of high-risk filmmaking," Turner said.

"When you're flying around in helicopters and airplanes, when you're in remote locations, you're dealing with weather — those are the sort of things that create the most risk in our profession, not the animals themselves. But they're the circumstances we have to work in," he said.

"We're trying to see things that haven't been seen before. Stay out in places people haven't been before. There are certain inherent risks in that. You mitigate those by knowledge and experience and Rob has all of that."

But what drives wildlife filmmakers like Turner and Stewart is the desire to share this knowledge of the wild with audiences.

"We just love the stories and the subjects that we're working with. We're totally connected and engaged with the wild and natural worlds around us," Turner said.

"It's really critical for us to understand what else is on this planet Earth with us. It's not just about us."

Environmental activists as well as peers in the documentary world are monitoring the search efforts for Stewart.

The conservation community is experiencing "a lot of nervousness" over Stewart's disappearance, according to Dustin Titus, a member of the board of directors for the United Conservationists Society of Canada who has known Stewart for more than a decade. "Everyone's really scared."

"Our thoughts and prayers go out to Rob's family and friends during this difficult time and we hope that the search efforts are as successful as possible given the circumstances," the Documentary Organization of Canada said in a statement posted online.