What is one observation method for natural navigation?

Subsurface formations serve as an effective observation method for natural navigation as they provide vital clues about the underwater environment. Divers can use the presence of reefs, wrecks, or other geographical features located beneath the surface to orient themselves and navigate through the aquatic landscape. These formations can often be seen from above when close to the surface or can be accessed by diving, offering a tangible reference point that aids in understanding one's surroundings.

In contrast, while current flow, water clarity, and depth readings are important features to consider during a dive, they do not provide direct markers for navigation. Current flow affects how a diver may drift but does not indicate position relative to the dive site. Water clarity can influence visibility but does not assist in orienting oneself in relation to specific underwater landmarks. Depth readings are crucial for safety and managing buoyancy, but they alone do not help a diver to navigate effectively without having a reference like subsurface formations.