The St Lawrence River is the longest inland seaway in the world. It took 350 years to transform it into the blue highway we now know. Within its history, the story of the deadliest narrows: the explosion of the biggest drilling barge in Canada in 1930: The J.B. King. 78 years after the accident, with a team of rebreather divers confronting the depth and current, Nathalie Lasselin embarks on a journey to identify the exploded wreck's remains and honor the memory of the international gravesite men. H2O secrets shares the mysterious underwater treasures. Below the surface a world of marine heritage, biodiversity and endless discovery awaits.