The 1-3 rule is a safety measure used in scuba diving. It states that divers should not descend more than one meter per second, and they should ascend no faster than three meters per second. This ensures that the diver does not experience decompression sickness or nitrogen narcosis due to rapid changes in pressure as they move through the water column. Additionally, this allows time for the body to adjust gradually and safely when moving up or down in depth. Following this rule helps keep divers safe during their dives and reduces risk of injury or illness associated with deep sea exploration.