Which piece of equipment is specifically made for propelling watercraft?

The piece of equipment specifically made for propelling watercraft is the paddle. A paddle serves as a manual tool that watercraft users, such as kayakers or canoeists, use to move their vessels through the water. It is designed to push against the water, enabling the user to either propel forward or steer. The construction of a paddle, typically with a long shaft and wide blades at either end, is optimized for generating thrust and maneuvering in aquatic environments.

In contrast, the other options serve different purposes. A helmet is designed for protection, particularly in activities where there is a risk of head injury. A leash is commonly associated with keeping a watercraft secured to a paddler, ensuring it does not drift away or can be easily retrieved if separated. A dry bag is a storage solution for keeping personal items dry while on the water, typically waterproof and designed to be sealed tightly. Therefore, the paddle distinctly fulfills the role of propulsion in watercraft, making it the correct answer.