A group of inseparable school friends from Odessa—Gleb, Kolya, and Vadim—discover a sunken sailing ship named Otvazhny ("Brave") and decide to raise it on their own. Gleb designs a lifting mechanism, but their geography teacher, Belov, suggests involving a larger team. The friends, however, insist on working independently, which leads to failure.
The idea of raising the ship captures the imagination of other students, who succeed in lifting the Otvazhny by pooling their efforts. Adults, including workers from a ship repair plant, also lend their support. The proud trio refuses to participate and instead plans to run away to a construction site. Their parents and teacher Belov intervene, convincing them to join the collective effort.
During a storm, Gleb saves the ship and is appointed its captain. The students embark on a journey across the Black Sea aboard the restored Otvazhny, uncovering its history along the way. The film concludes with their return to Odessa, marking the end of their adventure.
