What devices are most commonly used to help divers navigate underwater?

B. Compasses and dive computers are indeed the most commonly used devices for underwater navigation. A compass provides divers with a reliable means of determining direction relative to magnetic north, which is essential in an underwater environment where visual landmarks may not be present. Using a compass, divers can follow a specific bearing to ensure they reach their intended destination or return to their entry point efficiently.

Dive computers play a critical role in navigation as well. Besides tracking depth and time, many dive computers have features such as GPS capabilities that can assist divers in retracing their routes when they surface. These devices can calculate deco times and monitor conditions, contributing to overall dive safety and navigation efficiency.

The other options, while they serve important functions, do not primarily focus on navigation. Underwater cameras and tripods are typically used for documentation and surveying purposes rather than navigation. GPS units are not effective underwater due to signal loss, and surface marker buoys are more for signaling the location of divers to surface vessels rather than aiding in underwater navigation itself. Lastly, relying on marine life signs can be highly variable and subjective, making them less reliable for precise navigation.