Which hydrodynamic effects become more pronounced when approaching a pilot station?

• A. Cavitation
• B. Squat and sinkage
• C. Wave making
• D. Frictional resistance

Answer: (B)

When a vessel moves into shallow, confined waters near a pilot station, squat and sinkage become more pronounced. The flow under the hull is forced through a narrower, shallower gap, which speeds it up and lowers the pressure beneath the hull. That combination makes the ship sit deeper in the water (increase in draft) and can alter trim as you approach the channel entrance. The effect grows with speed and is amplified by reduced depth and restrictive surroundings like piers and banks, which is exactly what you encounter at a pilot station.

The other effects depend on different conditions. Cavitation is tied to very high local pressures and propeller flow, not specifically to approaching a pilot station. Wave making relates to hull speed and sea state, and frictional resistance depends largely on wetted surface and speed, which don’t inherently intensify just because you’re nearing the pilot area (and speeds are often reduced for maneuvering).