The opening war-torn scene shows underwater conflict between two ships during World War II. A missile slams into the USS Charlotte in 1944 off the coast of the British Virgin Islands, and as the ship catches fire, two crew members vanish beneath the waves—perhaps claimed by sharks lurking below. This harsh prologue threads into a present-day setup where Noah, Jack Parr, a professional diver, rides a speedboat across Caribbean waters with Levi, Julian Sands, his partner, as they discuss how their small diving venture has been squeezed by financial pressures. Noah plunges into the surf with excitement when he discovers a sunken vessel buried in the sand: the same USS Charlotte, now a relic about eighty years old. He decides to explore the gun tower and wander its interior, but a poor radio link and fading signals force him to retreat to the boat. Their elation at the find is tempered by practicality—the wreck won’t be a quick payday, and the local authorities and marine biologists must oversee its exploration before any tour can begin.
Five of Noah’s friends arrive to join the expedition, each quickly sketched: Brett, Alexander Arnold, the moneyed optimist; Sam, Kim Spearman, Noah’s romantic interest; and Riley, Erin Mullen, along with a few others, all ready to chase the next big dive. Levi, who keeps the drinks flowing, is blunt about their cash crunch and the looming need to cut costs, while Noah envisions a boost if Brett will fund broader access for the group to explore the Charlotte. Brett offers a quick $1,000 for a dive, but Levi resists at first; Noah suggests a bigger deal—$50,000 for the entire group to dive under his guidance, hoping to secure their future in the business. The plan hinges on permission from authorities and the safety of everyone involved, but the team is eager and the risk feels manageable.
The next morning, they load up for the Charlotte expedition, moving to the spot where the wreck lies. Noah emphasizes the need to stay close and avoid overconfidence, while the other divers, including Logan, Arlo Carter, slip beneath the waves. Inside the wreck, Noah anchors a guideline to a sturdy beam and instructs everyone to breathe slowly as they push deeper. The mood shifts from excitement to tension as they loosen up, playfully ribbing each other with a game of rock-paper-scissors while Brett lingers a bit longer than warned. The atmosphere grows uneasy when the guideline suddenly snaps and a sense of unseen danger—perhaps the presence of sharks—emerges.
The group loses their bearings as they press onward, the air supplies dwindling. Riley’s oxygen drops to critical levels, and a dead end traps them as they scramble upward. Logan’s mask is knocked loose, and a shark looms menacingly, forcing Sam to assist while Noah realizes the water is more perilous than they anticipated. A stifled panic spreads; another door opens to reveal sharks closing in, and Logan is fatally attacked. In a stark moment of decision, Brett suggests leaving Logan as bait to draw the predators away, a choice that underscores the desperate dynamics of the group under pressure.
With fear mounting, the team splits: Noah and Brett attempt to reach the surface, while Sam and Riley brace themselves in an air pocket to buy time. Riley’s remaining air supplies become a critical ticking clock, and Noah warns that they must move if the pocket’s air deteriorates. They encounter Logan’s remains and push forward, but rising danger remains as a second shark circles their path. A torn guideline and renewed shark attacks force Noah to improvise, using an air tank as a distraction to free himself from a tight spot beneath fallen beams before rejoining Sam in the pocket.
As the plan to escape unfolds, Sam and Noah rekindle a sense of purpose and focus. They navigate toward the munition chamber—the historic supply hub that once fed gun towers in the war—and hope to exploit a hidden route to freedom. Sam offers a farewell kiss to Noah before continuing the ascent. Back on the surface, Brett reaches the boat to warn Levi of the deadly predators still circling the wreck and the others’ precarious fate. The sharks prove relentless: Brett is attacked, his leg torn away before he vanishes beneath the waves.
Inside the wreck, Noah and Riley advance to escape, while Sam works to shepherd Riley toward safety. A dramatic turn comes when Levi, diving back into danger, resurges to rescue Noah, and Sam doubles back to trap a shark using a makeshift cage while Riley bleeds from a fatal wound. Levi fights bravely and is fatally bitten, leaving Noah and Sam to process the loss. In a final act of endurance, Sam completes the perilous exit and helps to bring Noah to the surface, where a new life awaits.
In a reflective coda set years later, Sam sails a speedboat along the coastline of New York as Noah sits in the back, knitting a cap for their newborn son, named Levi in honor of the friend they lost. The image closes on a hopeful note: a small family of three, built from love and memory, moving forward together in the wake of the tragedy. This ending hints at how their lives have rebuilt around resilience, partnership, and the shared dream that began beneath the remembered shadow of the Charlotte.
