Which of the following natural references can help with navigation?

Light and shadows serve as important natural references for navigation, particularly in underwater environments. Divers can use the position of the sun or the light filtering down through the water to gauge their orientation and direction. Light penetrates the water at different angles depending on the time of day and the water's surface conditions, which can influence visibility. Shadows created by objects underwater—like reefs, rock formations, or even other divers—can provide additional cues to help maintain a sense of direction. This method of navigation is often more intuitive and immediate compared to relying on electronic instruments, making it a valuable skill for divers to develop.

In contrast, temperature changes, surface pressure, and air bubbles do not provide reliable directional guidance. While temperature variations can indicate changes in depth or currents, they do not direct you towards a specific navigation point. Surface pressure can give divers an understanding of their depth, but again, it does not assist in directing their travel. Air bubbles may offer some insight into current direction when observing their path, but this is less effective than using light and shadows, as bubbles can be influenced by many factors including water movement.