What equipment is essential for conducting a proper rescue operation underwater?

A buoyancy control device and communication equipment are crucial for a proper underwater rescue operation. The buoyancy control device allows the rescuer to maintain neutral buoyancy when assisting a diver in distress, which is vital for managing both the rescuer's and the victim's safety and comfort in the water. This equipment helps prevent ascents or descents that could lead to further complications during the rescue.

Communication equipment is equally important as it ensures that rescuers can effectively communicate with each other, coordinating their efforts without confusion. In underwater situations, where visibility may be limited, and audio communication is challenging, having reliable communication tools can facilitate a successful rescue operation.

The other choices lack the necessary components that are fundamental for an effective rescue. A dive knife may be useful in specific situations, but it does not provide the overall control and communication capabilities required. A compass is helpful for navigation but does not aid in managing a rescue scenario. Regular swim goggles are insufficient for underwater visibility and do not offer the protection and functionality required in a diving context.