What is one of the minimum equipment pieces described for MK20?

Swim fins or boots are essential pieces of equipment for the MK20 because they facilitate mobility and efficiency while underwater. These items enable divers to navigate their environment effectively, reducing fatigue and enhancing propulsion when swimming. The design of swim fins helps divers conserve energy, making it easier to maintain stability and control while maneuvering in various underwater conditions. This is particularly important in rescue operations where quick and agile movements may be required to respond to emergencies.

In contrast, while the other equipment listed may have specific applications in diving scenarios, they do not serve as fundamental necessities for the MK20's operational efficiency as swim fins or boots do.