Diving bells

DID YOU KNOW?

Dry bells are used in submarine rescue missions; they form an airtight seal with the hatch to let crew escape

Diving bells

The pressurised compartment of these amazing sea vehicles allows divers to exit underwater

The diving bell is one of the earliest diving chambers, which dates back to the fourth century BCE. The traditional wet bell consists of a chamber, open at the bottom, which is attached by a hose to an air supply on the surface.

It functions in a similar way to a moon pool, with the air inside the diving bell pressurised by the weight of the seawater above. The pressure of the air is equal to the pressure of the water, preventing water from entering the diving bell, and allowing divers to enter and exit through the bottom.

As the bell descends and the pressure increases, the air inside is compressed, so a continual supply of fresh air is pumped in from the surface. A ballast helps to counteract the buoyancy of the air and keeps the bell steady, preventing any air from leaking out.

A modern dry bell is also pressurised, but is closed at the bottom by a hatch. The hatch opens inwards and is kept closed by the air pressure inside, allowing divers to come and go. Alongside the air supply, cables to the surface also provide power for lighting, tools and communication equipment.

Supply lines

Hoses and cables connected to the surface supply the bell with air, power and a means of communication.

Emergency gas

Should the main air supply malfunction, the diving bell is equipped with emergency tanks. A diving bell used by tourists at the end of a pier in Zinnowitz, Germany

Sphere

To maintain the internal air pressure, modern diving bells are made in a strong, spherical shape.

Pressure hatch

A hatch in the base of a dry diving bell allows the diver to enter and exit.

How low can they go?

300m

(984ft)

DIVING BELL

Mounted equipment

The internal chamber must be small to minimise the weight of the bell, so most equipment is attached to the outside.

A gas control panel found in a wet diving bell used for training

6,000m

(19,685ft)

10,000m

(35,756ft)

MIR SUBMERSIBLE

DEEPSEA CHALLENGER