Why is proper hydration critical before deep dives?

Proper hydration is critical before deep dives primarily because it helps in reducing the risk of decompression sickness. When divers are dehydrated, it can lead to a higher concentration of inert gases, particularly nitrogen, in the body. During a dive, as pressure increases, these gases are absorbed into the body's tissues. If a diver is dehydrated, the blood volume may decrease, which can affect how effectively nitrogen is carried away from tissues and eliminated from the body during ascent. This inefficiency can increase the likelihood of bubbles forming, leading to decompression sickness when a diver ascends too quickly or after staying at depth for extended periods.

Staying well-hydrated improves blood circulation and ensures that the body can more effectively manage gas absorption and elimination, contributing to a safer diving experience. While factors like buoyancy control, visibility, and dive time can be important for dive planning and execution, they do not have the same direct impact on health and safety as hydration does in relation to decompression sickness.