Final answer:
Predive observations such as the boat's orientation against the current, the sun's position, and fixed points like a moored buoy are valuable for natural navigation while diving. The depth information can aid in understanding the underwater landscape.
Step-by-step explanation:
The predive observations that may assist with natural navigation during the dive include: knowing the boat's orientation in relation to the current, as indicated by the divemaster; the position of the sun, which can provide direction based on the time of day; and the presence of fixed objects like a buoy moored behind the boat. The boat's depth finder indicating a depth of 15 meters/50 feet directly under the boat can also provide useful information about the underwater terrain you're exploring.
Using Currents for Navigation
If the boat is pointed directly into the current, you will know that swimming against the current will lead you back to the boat, which is helpful in planning your return route.
Using the Sun for Navigation
Knowing that the sun is setting in the west at 1530 hours helps determine the cardinal directions when you are underwater, which can assist in navigation.
Fixed Objects as Reference Points
A large buoy moored directly behind the boat serves as a reference point. By keeping track of your position relative to this fixed object, you can better gauge your direction and distance traveled underwater.