What is a critical factor to confirm before starting a dive?

Verifying the functionality of all diving equipment is essential before starting a dive because the safety and effectiveness of the dive depend heavily on the proper operation of that equipment. This includes checking the air supply, ensuring that the dive regulator is functioning correctly, and verifying that communication devices and flotation gear are in good condition. A malfunctioning piece of equipment can lead to dire consequences underwater, including potential accidents or emergencies, which could jeopardize the diver's safety. Ensuring all diving gear is in optimal condition contributes fundamentally to a successful and safe dive experience.

The other options, while important for overall dive planning and preparation, do not directly relate to the immediate safety mechanisms that equipment checks provide.