How long must a fast rescue boat be capable of maneuvering, and at what speed in calm water?

The correct choice indicates that a fast rescue boat must be capable of maneuvering for 4 hours at a speed of 20 knots in calm water. This requirement ensures that the boat can operate effectively for a sufficient duration to assist in rescue operations.

The specification of 4 hours is vital as it provides enough time to reach persons in distress and safely return to the ship or another location for assistance. Speed is equally important; 20 knots is a practical and effective speed that allows the rescue boat to respond swiftly to emergencies without compromising the safety of the personnel onboard the vessel.

In maritime safety, having a fast rescue boat that can operate at these parameters significantly enhances search and rescue capabilities, ensuring that they can reach victims quickly and perform necessary life-saving actions.