What do dive computers primarily determine?

Dive computers are essential tools in modern scuba diving because they primarily monitor and calculate the accumulation of inert gases in a diver's body during a dive. As divers descend, they are exposed to increased pressure, which causes inert gases, such as nitrogen, to be absorbed into their tissues. The dive computer continuously tracks these changes in depth and time, allowing it to estimate the levels of inert gas saturation within the body. This information is critical for preventing decompression sickness, also known as "the bends," by providing real-time data that informs divers when they need to ascend or make safety stops.

The other options focus on aspects that are not the primary function of dive computers. For instance, measuring surface temperature, calculating surface time, or assessing water clarity does not relate to the core function of tracking inert gas absorption, which is vital for a diver's safety during and after a dive.