What must be ensured for standby divers during diving operations?

For standby divers during diving operations, it is crucial that they must be able to access the water rapidly. This requirement is vital for ensuring safety, as standby divers are placed in a position to assist in emergencies or to provide support for divers who may encounter difficulties underwater. Quick access to the water allows them to react promptly, minimizing the risk of injury or fatality in the event of an incident.

Standby divers are essentially a safety measure, ensuring that help is readily available. The swift access to the water enables them to intervene as quickly as possible, which can be critical for the diver's safety oftentimes in situations where every second counts. Thus, maintaining a readiness to respond is a fundamental aspect of diving safety protocols.

Other choices do not align with the primary objective of ensuring the safety and readiness of standby divers. For instance, having them wait on the surface or taking breaks could significantly delay their response time.