Diving Bells
After snorkels, diving bells were the next successful method of increasing endurance underwater. These bells consisted of a weighted chamber, open at the bottom, in which one or more people could be lowered underwater. The early use of bells was limited to short periods in shallow water, but later bells became quite popular when inventors developed methods of supplying fresh air to the bell using barrels and hoses.

In the 19th century, the diving bell concept was put to use for underwater construction. Engineers used compressed air to keep water out of shafts or tunnels being dug underwater. Large airtight chambers called caissons were also used to shelter workers who carried out underwater construction projects such as building bridge foundations.

Diving bells continue to be used today as part of modern diving systems, providing a method of transporting divers to their work sites while under pressure and, once at the site, of supplying breathing gas while the diver works. Smaller diving bells called personnel transfer capsules (PTCs) are used to transfer divers from one place to another -- for example, from a ship to an underwater destination and back -- while maintaining high pressure.

To learn more, visit our Underwater Exploration website.