These are the cases in which the disturbance has been caused from outside and which are not connected to the diver directly. Both free and scuba divers might enmesh in fishermens nets or plants under water, get stuck in narrow openings under stones or in caves. Moreover, the ocean hides dangerous grenades, mines and bombs that have once been dropped into the water. That is why divers must not touch any object which seems suspicious or unknown. Besides, there are many sharp objects under water such as mussels and stones which might cause serious damage. Stepping on wet stones and rocks, overgrown with algae, is risky in terms of slipping or cutting.
Carelessness or lack of knowledge about fish might result in pricking on poisonous fish. Symptoms are different and sometimes the injuries lead to death. The most common symptoms are fever and fatigue. The pricked place should be tied tightly and made a cold compress to avoid the spreading of poison throughout the whole body. Rare situations, from which there might be no exit but death, are meeting dangerous creatures such as sharks. Everyone hopes that if he ever meets a shark, it will be the size of the one above.
In this case, pathology depends wholly on the diver and results from reasons connected directly with his or her body. It includes barotrauma of the ears and sinuses, eardrum ruptures and muscle cramps.
Muscle cramps are lasting convulsions of a group of muscles. They occur when a muscle is tired and not well-warmed up or when the movement is too jerky. The most common places of cramps are the muscles of the thigh and calf. Muscle cramps might be panicky for inexperienced divers. To avoid cramps, divers should not do intensive exercises before their muscles are warmed up. If these occur, however, here are two exercises to do away with cramps:
When there is a cramp in the foot, calf, or the back part of the thigh, grab the fin or your toes with your hands, straighten the knee and bend the foot to the front part of the leg below the knee.
When there is a cramp in the frontal muscle of the thigh, grab the ankle, pull it up to the back until the heel touches the back of the thigh.