What is an essential part of the dry suit?

The zipper is an essential part of a dry suit because it serves as the primary closure mechanism that keeps the suit watertight. A functioning zipper ensures that the diver remains dry by preventing water from entering the suit, which is crucial for thermal protection and overall comfort during dives. The integrity of the zipper directly impacts the safety and effectiveness of the dry suit.

In this context, while the zipper may indeed be expensive, its critical function cannot be overstated. A malfunctioning or ineffective zipper can compromise the entire suit, making it vulnerable to leaks and reducing the diver's ability to maintain body heat in cold water environments. Therefore, both aspects of being critical and potentially expensive highlight the importance of the zipper's role in the suit's overall functionality and safety.