As the Bajau descend beneath the waves, their bodies are adapted in unique ways to withstand the ocean pressure. Having little body fat reduces buoyancy, making it easy to dive deep without using fins. With every 10m descended, pressure increases by one bar – so at 30m below, the pressure is three times that of the surface. This puts extraordinary forces on the body. Ear pain is the first thing you notice. The pressure on the outside of the eardrum increases pushing it inwards. If the pressure isn’t equalised by holding your nose and forcing air into the middle ear, the eardrum will rupture. As you go deeper, the pressure increases on your lungs.
However, the body has a clever ‘blood shift’ mechanism – blood from other parts of the body is diverted to the lungs to equalise the pressure.
As you continue your descent, heart rate and metabolism slow and blood pressure increases, to use less oxygen. Diving deeper still then causes blood to be drawn away from your hands and feet and sent to your vital organs. Adding to the incredible adaptations for diving deep below the waves is mind control. Relaxation is key to allow the body to make all the necessary adjustments and to prevent hyperventilation. Many freedivers enter a meditative state by using deep-breathing techniques. The relaxed attitude of the Bajau suggests that this effect even translates into their everyday lives.