2. Pressure Decompression Sickness is when nitrogen bubbles form in blood which cause clots and tissue damage. Cause by a rapid decline in pressure and extra nitrogen molecules are inhaled gases inside lungs will expand and could block the circulation in your lungs air pockets in the ear canal are effected when water pressure squeezes the air in these spaces, causing a feeling of pressure and pain in your head and ears

3. Coldness Hypothermia is defined as a core, or internal, body temperature of less than 95°F Your blood circulation is now restricted only to organs because the body knows that those are the most important to keep warm but if treatment is not provided, organs will begin to shut down

4. Darkness The sun is the only source which vitamin D is produced and without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults