What action should be taken immediately if decompression illness occurs?

Administering oxygen immediately is the appropriate action when decompression illness occurs. This condition, also known as "the bends," results from nitrogen bubbles forming in the bloodstream or tissues as a diver ascends too quickly. Administering oxygen helps to reduce the size of these bubbles, assists in the elimination of nitrogen from the body, and provides critical support to the body's healing processes.

Oxygen therapy can decrease symptoms of decompression sickness and improve outcomes. It is vital for the diver to receive high-flow oxygen as soon as possible, ideally while other emergency procedures are initiated, such as arranging for transport to a hyperbaric chamber for further treatment. Prompt action can significantly influence recovery and mitigate potential long-term damage.

While the other actions listed might seem plausible, they could exacerbate the situation. For example, ascending to the surface can worsen the condition due to changes in pressure and further bubble formation. Swimming to the nearest boat may delay necessary treatment and risk additional complications. Ignoring symptoms, even if feeling fine at the moment, can lead to a worsening of the condition and delayed response to a serious health emergency.