Diving for sponges has been carried out in Greece since ancient times. The use of sponges was described by Aristotle and mentioned in both Homer's Iliad and the Odyssey. For centuries now the Greek sponge trade has focused around the Dodecanese, with one indisputable epicentre - Kalymnos, the sponge divers' island. Finding sponges, diving to harvest them from the ocean bed and selling them throughout the world is a commerce in which Kalymnos has excelled.

Sponges, are not plants but aquatic animals, metazoans to be precise, attached to the ocean bed. Their surface has thousands of pores, which constantly take in enormous volumes of water, extracting bacteria for their food. They therefore act as valuable biological filters of seawater. There are many different species of sponge, but only five main commercial types. No man-made material compares with them for cosmetic, bathing, household, painting and ornamental use.

When fresh from the sea, sponges are black and quite unappealing. As soon as the diver brings them up to the boat, they are vigorously pressed by foot to remove the liquids from the pore canals and tissues. They are then washed and immersed in the sea for two hours, pressed and washed once more and finally beaten with the branches of palm trees to remove any foreign bodies. Overnight, the sponges are immersed in the sea in a net and this process is repeated until the external membrane and tissues are broken down, leaving only the skeletal fibres. The sponges are then trimmed at the base and left to dry, either on the deck or hanging from the mast of the boat. Once dry, they are pressed, placed in sacks and sent to the merchants. At the merchant’s workshop the sponges are trimmed to the required sizes and treated by immersion in water and hydrochloric acid, to make them golden, and in potassium permanganate if a really blonde colour is preferred. This process produces a sponge that is ready for use - clean and fresh, with a pale colour and a nice soft feel.

Although sponge diving was a source of income for several Greek islands during the last centuries, Kalymnos is known to be the center of the Greek sponge diving industry. The waters around the Greek islands are very suitable for the sponges to grow, because of the high temperature. The best sponge quality is found in the southeast of the Mediterranean sea.

In Kalymnos, sponge diving has it’s roots since ancient times. It can be seen as the oldest profession on the island. Diving for sponges brought social and economical development to the island. 

In the old days the “skin diving” method was used. The crew went out to sea in a small boat. They used a cylindrical object with a glass bottom to search the ocean floor for sponges. As soon as one was found, a diver went overboard to get it. He was usually naked and carried a 15 kilogram flat stone, known as the “skandalopetra” with him to take him down to the bottom quickly. The diver then cut the sponge loose from the bottom and put a special net around it. Depth an bottom time depended on the divers lung capacity. They usually went down to about 30 meters for 3 to 5 minutes.

Although this was very hard work, this way of diving brought so many sponges to the island that the trade from Kalymnos expanded in a great way around 1800. Halfway the 19th century Kalymnos had several merchants that became very wealthy. Through the big profits they made on the sponges they also gained a big influence on the social life on the island.

As from 1865 trading sponges became “booming business”. The reason for this was the introduction of the standard diving suit or Skafandro as the Greeks call it. A merchant from the island of Symi brought equipment, probably Siebe Gorman, to the island. The advantages seemed enormous. Now, divers could stay down as long as they wanted in greater depths. The best sponges could be found at depths of about 70 meters. A diver could now walk on the ocean floor and look for them. 

Due to the standard suit the sponge trade got an unlimited growth. From Kalymnos, ships sailed the Aegean sea and the Mediterranean sea. They sailed as far as Tunisia, Libya, Egypt, Syria and Lebanon. They stayed out at sea for at least 6 months.

The profit on the sponges was high. For the divers the working circumstances were better than diving naked. However, there was a big danger in staying down deep for long times: decompression sickness. Soon after the standard suit was introduced, the first casualties appeared. The symptoms, heavy pain, paralysis and eventually death must have been terrifying for divers and other crew because they did not have a clue what caused all this!

A combination of several dives a day to depths up to 70 meters and then coming up without decompression stops did not miss its devastating effect: in the first years the standard suit was used, about half of the divers got paralysed or died of decompression sickness. Between 1886 and 1910 about 10.000 divers died and 20.000 got permanently disabled.

In the beginning of the 20th century the sponge diving industry had hard times in the Dodekanesos. Around 1900 the growth got to her maximum and both world wars caused limitations to the trade. From Kalymnos and other islands like Halki and Symi large groups of divers settled in other parts of the world to do what they did best: diving.  Around 1905 a group of about 500 divers from the Dodekanesos settled in Tarpon Springs, Florida, USA. These days diving helmets are still made by Nicolas Toth. Nic is the grandson of Antonios Lerios, born on Kalymnos, who settled in Florida in 1913 as a helmet maker.

After the second world war the sponge diving industry almost completely stopped in the Dodekanesos. In those days Australia refused to work together with Japanese divers in the pearl industry. Therefore many Greek divers settled in Australia.

Many people feel that the introduction of the synthetic sponge meant the end for the sponge diving industry. The biggest problem however, occurred in 1986. Nearly all the sponges in the Aegean sea turned out to be infected. The cause of this never became clear. A sudden rise of the water temperature could be the cause. Similar infections appeared in the Gulf of Mexico in the 1940’s 70’s and 90’s. 

Today there is hardly anything left of the sponge diving fleet from 1868. From 400 ships, about 10 to 15 are left. In recent years the sponges in the waters around Kalymnos have recovered in a great way. However, local sponge divers announced that they encountered infected sponges again in October 2000.