Tati is a typical teenager, unable to learn mathematics, but very intelligent when creating plans to escape the punishment of the mother. During the summer, she needs to hide that she has to do math classes to improve her grades, conquer Zeca, the most popular boy in school and also care for the heartache of her mother, who wants to try to find a new love.

From its origin in the Serra do Mar to its end in the Atlantic ocean, this documentary highlights the problems that one of the main Brazilian rivers face along its more than 1,000 kilometers in the states of São Paulo and Rio de Janeiro.