The Meg (2018)

Jonas Taylor is a rescue diver who attempts to save the crew of a damaged nuclear submarine as the hull is being rammed by an unidentified creature. Two of his crew members become trapped in the sub, and Jonas sees that attempting rescue would result in the deaths of everyone they have already saved, so at the cost of the loss of two of his colleagues, he leads them to safety. When he tells his story later, it is dismissed by another survivor, Dr. Heller, who denounces him, saying that he was psychotic.

Five years later, billionaire Jack Morris meets Dr. Minway Zhang at the underwater research facility Mana One, which Morris is funding. Zhang and his oceanographer daughter Suyin supervise a mission to explore a deeper section of the Mariana Trench, previously concealed by a thermocline of hydrogen sulfide. The submersible is piloted by Japanese scientist Toshi, American scientist "The Wall," and Jonas' ex-wife Lori. They are attacked and trapped by a large creature.

Zhang and Jonas' old friend and Mana One operations manager, James "Mac" Mackreides, venture to Thailand to recruit Jonas, now a loner. Suyin attempts the rescue but is attacked by a giant squid that is subsequently killed by an enormous shark. Jonas goes down to save the crew; Toshi sacrifices himself to help the others escape.

The Mana One crew discovers that the giant shark is a Megalodon or "Meg", a prehistoric species of shark previously believed to be extinct for over two million years. When they realize the Meg has escaped the thermocline, they resolve to kill it, knowing modern humans are unequipped to deal with such an ancient creature. After Jonas marks it with a tracker, Suyin enters a shark-proof tank to shoot the meg with poison, which succeeds in killing the creature.

However, a second, larger meg (revealed to be the one they encountered in the trench) emerges, devouring The Wall and the dead Meg. It critically wounds Zhang, and Dr. Heller sacrifices himself to save another crew member. Zhang dies on the way to rescue.

Morris tells the crew that he has informed all neighboring governments about the Meg and they are sending military units to handle the Meg. However, hoping to keep the Meg a secret, he instead enlists a mercenary team to kill the Meg with depth charges. The team fails, and the Meg eats Morris.

Jonas and the surviving crew members learn that Morris lied - no military ships are coming to help them. They decide to kill the Meg themselves and with apprehension plot the destination of Megs's route of travel, Sanya Bay, a China beach crowded with swimmers.

The Meg attacks swimmers at Sanya Bay. The crew lures it away with recorded whale sounds, An undersea fight ensues and Jonas wounds the Meg with his submersible and stabs it in the eye, crippling it. Its blood attracts a shiver of modern sharks that devour the dying Meg. Jonas and the crew celebrate their survival.