Which of the following is NOT a type of permanent line?

In cavern diving, permanent lines are established for safety and navigation, enabling divers to find their way in complex underwater environments. Among the choices provided, the rescue line does not represent a permanent line type. Instead, it typically refers to a temporary line or equipment specifically employed during rescue operations. Its purpose is to facilitate quick access or retrieval during emergencies, rather than to remain fixed in place as a permanent feature.

In contrast, the gold line, exploration line, and secondary lines are recognized types of permanent lines. These lines are usually installed in dive sites to create a reliable reference for divers, enhancing safety and guiding them back to the entrance of the cavern. The gold line often signifies the primary route for navigation, while exploration and secondary lines help divers safely navigate specific areas or support multiple divers in the same environment. Understanding the distinctions between these line types is crucial for safe cavern diving practices.