The family of a Canadian filmmaker and conservationist who died during a shark filming excursion off the Florida Keys filed a wrongful death lawsuit Tuesday.

Rob Stewart, 37, of Toronto, Canada, died while diving in January off the coast of Islamorada, Florida, to film a follow-up to his 2006 documentary "Sharkwater," which examined the impact of shark hunting on the ocean's ecosystem. He also made a 2013 documentary "Revolution" about environmental collapse and was a wildlife photographer.

According to the lawsuit, Stewart and dive organizer Peter Sotis both surfaced at the same with apparent breathing difficulties, but Stewart didn't make it back on board the dive boat. While others were treating Sotis, they allowed Stewart to slip away.

Stewart's submerged body was found three days later, about 300 feet from where he was last spotted on the surface, following a massive search involving the Coast Guard and several other agencies.

Stewart's death "was a preventable tragedy that was going to happen to someone," his family's attorney, Michael Haggard said in an email.

The family "hopes the legal action will push out and/or change the ways of all irresponsibly operating diving businesses and help keep attention on Stewart's mission of ocean conservation," he added.

Unspecified damages are being sought in the negligence lawsuit filed in Broward County, Florida, Circuit Court. It names as defendants Horizon Dive Adventures of Key Largo, Florida, Add Helium LLC of Fort Lauderdale, Florida and dive organizers Peter and Claudia Sotis, who operate Add Helium.

An attorney for Sotis did not immediately respond to an email seeking comment.

According to the lawsuit, the dive was taking place at the wreck of the Queen of Nassau in about 230 feet of water and about six miles from the Islamorada coast. A grappling hook had been placed on the wreck that was attached to a surface buoy to mark the location of the dive. Stewart and Peter Sotis encountered difficulties when they went down a third time to remove the grappling hook.

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