High school student Sasha was looking forward to the weekend to break away with her friends, but her parents ordered her to go on a water excursion with her half-sister Mia. Having decided that the prospect of spending several hours on a ship with harmful classmates, who constantly bully Mia, does not appeal to them, the sisters and Sasha’s friends set off to explore the underwater cave. But the planned entertainment soon turns into a nightmare - in a confined space, divers will have to escape from bloodthirsty sharks.