Two commercial diving jobs in the Baltic Sea make up this film, both handled by the Baltic Sea Divers team. In Warnemünde, trainee diver Eustus gets his first solo assignment, taking ultrasonic thickness measurements on the riveted steel hull of the aging fish cutter Rollmops to check how much of the metal corrosion has eaten away. At the same time, the crew aboard the vessel BT2 works near the Fehmarn Belt Tunnel construction site, sending down a remote-controlled vehicle to inspect conditions too deep or too risky for a diver to reach directly. The film cuts between the two jobs, showing the physical strain and precision of hands-on underwater inspection against the quieter, camera-fed work of operating an ROV from the surface. Along the way it covers the practical mechanics of the trade: how divers read instruments through gloves and low visibility, how a training dive gets signed off, and what a tunnel project this size demands from the people checking its underwater welds and steel.