On a warm day in Northern Australia, Grace, her husband Adam, and her younger sister Lee decide to take a fishing tour through the dense mangrove swamps, hoping for a relaxing escape. They join a local tour called “Blackwater Barry’s,” though their guide Jim is unavailable and they instead get Jim’s colleague to lead them. The swamp is quiet, remote, beautiful, but there is an undercurrent of danger—crocs are known to inhabit the waterways, though the guides assure them that none are unusually aggressive at the moment.

As the boat winds deeper into the mangroves, the tourists attempt to fish, enjoy the quiet. The tension builds when they drift farther from help, and the environment begins to feel less benign. Then suddenly the tranquility shatters. A huge saltwater crocodile bursts from beneath the boat, capsizing it, and in the violent chaos Jim is killed. Grace, Lee, and Adam manage to scramble out of the wreck into the murky water, fighting fear and shock. They make their way to a nearby tree, climbing up to avoid both the water and the crocodile, which circles below, unseen but very present.

Marooned up in the branches, the three survivors must wait and decide how best to stay alive until rescue arrives — though it seems rescue may never come. The crocodile stalks them in the water beneath, sometimes visible, sometimes hidden under muddy water or among roots and branches. The environment is oppressive: heat, insects, the rising possibility of dehydration, starvation, or injury. As night falls, danger increases, both from the predator and from the harsh elements.

Adam tries to find a way to help the group escape. He makes various attempts to use what remains of their boat, to reach land, to signal for help, but each plan is thwarted. At one point, Grace is bitten, her condition worsens. The tension among the group grows—not only fear of the crocodile, but worry about whether they will make the right choices, whether they will cost each other lives.

As the ordeal drags on, they must make a desperate decision. Lee (the younger sister) realizes that some chance of survival depends on taking action rather than waiting. Eventually she arms herself with a revolver they have, attempts to kill the crocodile. In that confrontation, she manages to shoot the beast. But not all are spared: Adam and Grace suffer fatal wounds in the process. With the crocodile finally neutralized, Lee crawls through the water, exhausted, traumatized. She makes her way back toward safety, carrying their memories and loss.

The film ends without full closure: Lee survives, but she is alone, changed. The swamp that seemed tranquil and exotic has revealed itself as ruthless and indifferent. Black Water leaves the viewer with an image of how fragile human life is in the face of nature’s power—and how the decisions made in moments of fear and pain can define whether one survives.