When should a diver use a dive slate?

Using a dive slate primarily serves the purpose of communication and note-taking underwater, which is why this choice is the most suitable answer. Underwater, verbal communication is impossible due to the environment and the breathing apparatus. A dive slate allows divers to effectively share information with their buddies—such as conveying essential messages about navigation, changes in plans, or even just sharing interesting observations about the surrounding aquatic life. Additionally, a dive slate can be used for jotting down notes that a diver may want to remember for later, such as safety observations or specific dive site details.

Other options involve functions that a dive slate is not designed for. While measuring depth and tracking water temperature are critical aspects of diving, these tasks are typically handled by dive computers or gauges. Storing an extra oxygen supply is also outside the function of a dive slate, as divers rely on their tanks and associated equipment for breathing support rather than a slate, which serves more of a communication purpose.