Underwater Explosions

While explosions anywhere are dangerous, they become increasingly more dangerous when they are underwater. On land it is able to mark where the explosions are so they are visible to the cast and crew, but when the explosive devises are under water, it is much more difficult to see them. While cork may be set to float about a devise that does not guarantee that the actors or stuntmen will see them, so it is up to the detonator to determine if the actor is at a safe distance from the explosive.

Large amounts of water have to be moved to create explosions under water, so industrial high explosives are used rather then black powder, which is not strong enough to create the effect. They have the be securely fastened to the bed of the river or sea and must be kept at the right depth. If it is too far under water, not enough water will be thrown into the air, if it is too shallow, the explosion will blast the water too far. Due to these factors and the need to have the devices within inches of the correct depth, it is important to have a huge knowledge of the local wave patterns.

Explosions under water create a shock wave which travels with much greater force then it would in the air. So it is imperative that personnel and other individuals won't be within the shock wave of the blast. Often small explosions or ultrasonic equipment is used to scare away local sea life to protect them from the shock wave.

Another option to create an underwater explosion is to use an air mortar. This is often used if it is too dangerous to use the high explosives or when filming in a studio tank. Air mortars have reservoir of compressed air that is released when a valve is opened.