The main activity of Kalymnian population for hundreds of years now has been the diving for sponges and their process and commerce.
Starting from Kalymnos with 6-17 meters boats, the diving was done in the whole Mediterranean Sea (Cyprus, Syria, Egypt, Libya, Tunisia, Morocco, Italy and Greece)

In various periods Kalymnian sponge divers moved in countries with more rich sea beds and created colonies. The most important of them is Darwin Australia and Tarpon Springs Florida USA including TAMPA and KEY WEST while smaller groups moved in France, Japan and Philippines.

Kalymnian traders controlled more than 70% of sponge commerce worldwide. The most important trader was Nikolas Vouvalis who had his base on Kalymnos and London England and branches in Cuba, Florida USA, Nassau Bahamas and the Greek islands Aegina, Simi and Chalki.

Beginning of the 50ies the synthetic sponge appeared and despite it's low quality, it replaced the natural sponge in many uses because of its low price .

Early 70ties, most of Africa Mediterranean countries nationalized their marine resources and suspended sponge diving. Since then, the sponge diving with Kalymnian boats takes place only in Greek seas, while individual divers go for diving in Libya and America under local companies.

In 1986 an epidemic destroyed almost all Mediterranean sponges. Since then, Kalymnos Island is the only island left in Greece where sponge divers still exist. They dive for sponges and shells.

Kalymnian traders still process and commerce local production sponges along with imported sponges from other Mediterranean countries, USA and Cuba.

Sponge fishery is done with a variety of ways. But the most effective utilised method is diving.
In sponge diving all known methods were utilised along with the diving equipment progress.
In the beginning it was free diving with Skandalopetra or "revera" and then "helmet", "fernez", "bottles" and "nargile".
In our days the diving methods "revera freediving" and "nargile" (continuous support of air from a compressor on the boat) are used by sponge divers.