When diving at an altitude above 300 meters you must?

When diving at an altitude above 300 meters, you must consider the effects of reduced atmospheric pressure on your body, which can increase the risk of decompression sickness. It is essential to adjust your dive plan, including depth and time, and to make necessary decompression stops during ascent. Additionally, using a dive computer or tables specifically designed for high-altitude diving is crucial to ensure safety. Always consult with dive professionals experienced in altitude diving before planning such dives.