Penguin In A Diving Suit

Levels of training and types of equipment and breathing gases used differ between types of diving.
History
Underwater diving for commercial, rather than recreational purposes may have begun in Ancient Greece, since both Plato and Homer mention the sponge as being used for bathing. The island of Kalymnos was a main centre of diving for sponges. By using weights of as much as 15 kilograms (33 lb) to speed the descent, breath-holding divers would descend to depths up to 30 metres (98 ft) for as much as 5 minutes to collect sponges.