What instrument is most reliable for making a controlled ascent in low visibility?

A dive computer with a back-lit display is the most reliable instrument for making a controlled ascent in low visibility conditions. This is because dive computers are specifically designed to track depth, time, and other important dive parameters, providing real-time data essential for safe diving practices. The back-lit display enhances visibility in dark or low-light environments, allowing the diver to easily read the information even when visibility is poor.

Additionally, dive computers typically include ascent rate monitors and alerts, which can help prevent dangerous rapid ascents. This feature is crucial when visibility is limited, as divers may struggle to gauge their ascent rates without reliable instruments. In contrast, a compass does not provide depth information, an underwater camera is not suited for monitoring ascent rates or depth, and while a manual depth gauge can be useful, it lacks the advanced features and easy-to-read display that a dive computer offers, especially in challenging visibility conditions.