Free-diving risks

Shallow water blackout

With increasing depths the oxygen pressure in the lungs will raise and will lead to the blood carrying more oxygen. When ascending to the surface the O2 pressure drops dramatically and when the pressure in the lungs is lower than the blood pressure, the oxygen will pass from the blood into the lungs leaving more affected area without oxygen, such as the brain.

This will get you unconscious and to start your descend in the ocean depending on the weights.

Do free-diving always with a buddy.

Sinus squeeze

With infections or any cold, you have difficulty in pressurizing. A sinus squeeze and eardrum explosion may occur leading to pain and maybe some damage.