Long before scuba, people dived for sponges. The soft skeletons of a few sponge species were valuable enough, for bathing, cleaning, medicine and industry, that whole island communities built their economies on retrieving them from the seafloor. The history of sponge diving is a history of extraordinary human endurance, deadly technology and migration, and it connects the Greek islands of the Aegean with the Gulf coast of Florida.

Key West, one of the places I’ve dived, was the first centre of Florida’s sponge trade in the 19th century, long before it was known for wreck diving and the Vandenberg. The trade shaped the Gulf coast as much as the Aegean islands. This page traces the story from the Greek free divers to the hard-hat era and the trade today.

Why sponges were worth diving for

Only a few sponge species make good commercial sponges, and they were once among the most valuable things the sea produced.

Most sponges have hard skeletons of mineral spicules. A small number of demosponges, mainly in the genera Spongia and Hippospongia, have skeletons made of a soft, springy protein called spongin, which becomes a durable, absorbent material once the living tissue is removed. Before synthetic sponges, these natural sponges were used for bathing, cleaning ships and houses, padding armour, applying paint and pottery glazes, and in medicine and surgery. The ancient Greeks wrote about sponges and sponge divers, and the Mediterranean trade is thousands of years old; see Mediterranean sea sponges and our guide to natural bath sponges.

The free divers of the Dodecanese

For centuries, sponge divers from the Dodecanese islands of Greece, especially Kalymnos and Symi, dived on a single breath holding a flat stone.

The stone, called a skandalopetra, was a smooth, flat piece of marble or granite weighing roughly 8 to 15 kilograms, attached to a rope tied to the boat. The diver held it in front of him and used it as a weight and a rudder to plunge quickly to the bottom, sometimes 30 metres or more, then cut sponges and placed them in a net before being hauled up by the crew. Divers trained from childhood and some could stay down for several minutes. The technique survives today as a free-diving competition discipline. The work was brutal: divers made dive after dive through the day, in cold water and with no protection from the pressure on their ears and lungs, and many suffered permanent hearing damage. Skill, strength and the ability to hold a breath were the difference between a good season and a poor one.

The most famous skandalopetra diver was Stathis Chatzis, a sponge diver from Symi. In 1913, when the Italian battleship Regina Margherita lost an anchor in deep water off Karpathos, Chatzis made a series of breath-hold dives and reportedly reached a depth of around 70 to 80 metres to attach a line to it, an astonishing feat that drew the attention of naval officers and scientists. Sponge divers were also responsible for one of the great archaeological discoveries of the 20th century: in 1900 divers from Symi found the Antikythera wreck, which yielded bronze statues and the Antikythera mechanism.

The skafandro: a deadly new technology

In the second half of the 19th century, the standard hard-hat diving suit, called the skafandro in Greek, reached the sponge fleets.

With a copper helmet, a canvas suit and air pumped from the surface, a diver could stay on the bottom far longer than a free diver and work deeper beds. Catches rose dramatically. But nobody understood decompression. Divers who stayed deep for long periods and came up quickly suffered from what we now call decompression sickness, or the bends: crippling joint pain, paralysis and often death. In the decades after the suits were introduced, large numbers of Greek sponge divers were killed or permanently disabled. On Kalymnos and other islands, many families lost men every season, and there was strong opposition to the suits; at times local authorities and the church tried to restrict them. The tragedy only eased in the 20th century, after the physiologist John Scott Haldane developed staged decompression for the British Royal Navy in 1908 and safer practices slowly spread.

As a diver, this part of the story stays with me. Every time I check a dive computer or make a safety stop, I’m benefiting from rules that were learned at a terrible cost by men like the sponge divers of the Dodecanese.

Key West and the hookers of Florida

Florida had a sponge trade long before the Greeks arrived, but it worked very differently.

In the 19th century, Key West was the centre of a sponge industry based on “hooking”. Spongers worked from small boats in shallow water, looking through glass-bottomed buckets to spot sponges on the seafloor, then pulling them up with long poles tipped with hooks. The sponges were left to rot on land or in pens in the shallows, beaten and cleaned, and sold at auction. Sponge beds stretched from the Keys up the Gulf coast and across to the Bahamas. Over time, the centre of the Florida trade moved north to the rich sponge beds off Tarpon Springs, near Tampa Bay.

Tarpon Springs: the Greek sponge capital of America

In 1905 a Greek sponge buyer, John Cocoris, brought Greek divers and diving equipment to Tarpon Springs, and the town was transformed.

The Greek divers in hard-hat suits could harvest deeper beds than the American hookers, and they arrived in large numbers from Kalymnos, Symi, Halki and other islands. Tarpon Springs grew into one of the busiest sponge markets in the world, with a sponge exchange, fleets of distinctive sponge boats and a thriving Greek community. Tensions with local hookers sometimes ran high, but the Greek method won out. At its peak in the first half of the 20th century, the Tarpon Springs sponge industry was worth millions of dollars a year. The 1953 film Beneath the 12-Mile Reef was set among its sponge divers.

The industry was then hit by a series of blows. A disease outbreak in the late 1930s killed most commercial sponges across the Caribbean, the Bahamas and Florida, red tides devastated the beds in the following years, and after the Second World War cheap synthetic sponges took over most of the market. By the 1950s the boom was over. Tarpon Springs still has a sponge docks district, a small working fleet, sponge shops and one of the highest proportions of Greek Americans of any US city, and its Epiphany celebration, in which young men dive into a bayou to retrieve a cross, is famous throughout the Greek diaspora.

Decline in the Mediterranean

The Greek sponge fleets also faced decline in the 20th century.

For generations, Kalymnian sponge boats sailed every spring to the sponge beds off North Africa, especially Libya and Egypt, and returned in autumn, an expedition that shaped island life. Political changes closed many of those grounds, overharvesting depleted others, and synthetic sponges undercut prices. In 1986 a disease outbreak swept through Mediterranean sponge beds, killing a large share of the commercial sponges in the eastern Mediterranean. Kalymnos still celebrates its sponge-diving heritage in museums, festivals and shops, and a small number of divers continue, but the industry is a fraction of its former size, kept alive as much through heritage and tourism as through harvesting.

Sponge diving today

Natural sponges are still harvested, mainly for bathing, cosmetics, art and as a niche eco-friendly product.

Modern sponge divers usually use surface-supplied air or scuba, and responsible harvesters cut sponges above the base so they can regrow, observe minimum sizes and rotate harvesting areas. Florida regulates commercial sponge harvesting with size limits and licences, and sponge farming, growing cut fragments on lines in the sea, has been tried in several countries, including small-scale projects in Micronesia and elsewhere. Our pages on whether sea sponges are alive and menstrual sea sponges cover some of the modern uses and concerns. If you visit Tarpon Springs or Kalymnos, the museums and sponge docks give a vivid picture of a trade that once employed thousands of divers and sent them to depths no recreational diver would visit today.