Once an important source of wealth in the Greek islands. The sponge industry was centered in the Dodecanese island of Kalymnos. A variety of social and environmental mishaps led to the near collapse of Greek sponge fishing by the 1980s.
These and more via the totally committed people at divingheritage.com
(I decided to be very slightly lazy about preparing posts before I go on vacation, so this will be the first in a short series featuring traditional industries of Greece, which is where I am right now).