Why do thunderstorms die over lakes

How can I protect myself from lightning while swimming, diving and water sports?

Lightning energy

Lightning currents vary in a wide range from a few kilo-amperes to a few hundred kilo-amperes. In the case of very brief processes such as lightning, the energy converted in the body is decisive for the risk to persons: from around 10 joules occurs Ventricular fibrillation a. For swimmers and divers, however, the danger is also through panic to consider, which can be triggered with energy values ​​well below these 10 joules.


  • In the case of a strong lightning current (200 kA), the 10 joule value becomes greater than 40 m fell below the point of impact.
  • With a medium lightning current (30 kA), the 10 joule value becomes around at a distance of 15 m fell below the point of impact.
  • Even in 100 m Distance, depending on the strength of the lightning bolt, an unpleasant to painful electric shock is felt, which can lead to a panic reaction.

Since the lightning current spreads radially in all directions in the water from the point of impact, it does not matter whether a swimmer is observed on the surface of the water or a diver in the depths (at the same distance from the point of impact).


In the usual Diving depths from 10 m to 20 m almost every lightning strike that strikes roughly above the diver is immediate life threatening!

Recognizing the risk of thunderstorms can be a problem during longer dives. When preparing for the dive, you can rely on the weather forecast and weather observation (first clouds appearing). It is also helpful to have a look at the lightning maps available on the Internet, from which the drawing up and direction of movement of storm fronts can be seen.
A short-term warning can also be given by a buddy who remains on the surface.