They Fill a River to Move This Ship

From the video's description

Meyer Werft builds huge cruise ships in Papenburg, Germany, far from the sea. The only way out is a small river, the Ems, and it is not deep enough. So near Emden a huge gate (the Emssperrwerk) closes and the water cannot flow out. Behind it the river rises up to 2.7 m above sea level, two small boats pull the ship backwards to the gate, and then it turns around and goes out to sea. The 3D ship, boats and gate are schematic.