The film is on course to cross C$1m in Canada after launching there recently, and follows Stewart as he highlights the threats faced by sharks from poachers and explores wider conservation issues.
Stewart shot Sharkwater in High Def in 15 countries over the course of five years.
'We are in a fortunate position to be coming to Cannes with a film that has already broken box office records in its first theatrical release,' Horizon Motion Pictures president Rob Straight said.
'The film succeeds because it's a gripping adventure with spectacular photography as well as a contemporary environmental warning.
Horizon's Cannes slate includes: Arturo Perez Torres' Super Amigos, which profiles a group of lucha libre wrestlers turned social activists in Mexico City; Anthony Gilmore's Behind Forgotten Eyes, which tells the stories of Korean women forced into sexual slavery during the second world war; and Juvies, an investigation of the US justice system, narrated by Mark Wahlberg.