A sponge diver is someone who harvests natural sea sponges from the ocean floor, traditionally by diving to depths of 30 to 200 feet on a single breath of air. For thousands of years, this was one of the most physically demanding and dangerous occupations in the Mediterranean world, centered on the Greek islands where rocky volcanic land left few alternatives for making a living. While the trade has declined sharply, it shaped entire communities and even migrated across the Atlantic to the Gulf Coast of Florida.
How Sponge Diving Works
Natural bath sponges grow on the seafloor, and someone has to go get them. The oldest method is pure freediving: no tanks, no air supply, just lungs and nerve. A crew would head out in a small boat equipped with a cylindrical glass-bottomed viewing box, pressing it against the water’s surface to scan the bottom for sponge colonies. Once a bed was spotted, the diver went in.
The traditional Greek technique uses a tool called a skandalopetra, a flat slab of marble or granite weighing 12 to 15 kilograms. The diver grips the stone, takes a final breath, and drops feet-first into the water. The weight pulls the diver down at one to two meters per second, fast enough to reach the bottom in seconds without wasting oxygen on swimming. At depth, the diver uses a hooked tool to cut sponges free from the rock, stuffing them into a net bag. When finished, a tug on the rope signals the crew above to haul the stone back up while the diver kicks toward the surface.
A typical dive lasted one to two minutes of working time at the bottom, with total submersion of two to four minutes depending on depth. Surface intervals between dives ranged from two or three minutes on shallow dives to ten minutes after deeper ones. Historical accounts describe Greek divers routinely working at 100 to 200 feet on a single breath, staying underwater for two to three minutes. Legendary divers from the island of Symi reportedly reached 240 feet.
The Sponges Themselves
Not every sponge on the seafloor is worth harvesting. Sponge divers target specific genera, primarily Spongia and Hippospongia, which produce the soft, absorbent bath sponges that have been used for bathing, medicine, and painting for millennia. The most commercially valuable Mediterranean species include Spongia officinalis (the classic “bath sponge”), Hippospongia communis (the “horse sponge”), and several smaller varieties. Other sponge genera growing in the same waters, sometimes called “wild sponges,” have no commercial value and are left on the bottom.
These target species typically grow at depths of around 10 to 30 meters, though some beds extend deeper. After harvesting, sponges are cleaned, dried, and trimmed. What reaches the consumer is the soft skeletal framework of the animal, stripped of its living tissue.
Kalymnos: The Island Built on Sponge Diving
The Greek island of Kalymnos became the world capital of sponge diving largely because it had no other option. Only 18% of the steep volcanic island could be farmed, so islanders turned to the sea. Sponge fishing may have been the oldest occupation on Kalymnos, and it drove the island’s social and economic development for centuries. Homer and Plato both mentioned sponges as everyday bathing tools, suggesting the trade was already well established in ancient Greece.
Sponge diving on Kalymnos was seasonal work. Each spring, the fleet departed for months-long voyages across the eastern Mediterranean, as far as the coasts of North Africa. The departure was marked by community celebrations, and the return of the fleet (or the news of who hadn’t survived) defined the rhythm of island life. Today, Kalymnos maintains three museums dedicated to the occupation, and sponge diving remains part of local identity even though far fewer people practice it.
The Industry Crosses the Atlantic
In the late 1800s, the sponge trade jumped to Florida. The natural sponge industry in Tarpon Springs dates from about 1890, when John K. Cheyney launched the first sponge fishing boat there. At first, sponges were retrieved by hooking them from the surface with long poles. That changed in 1905 when John Cocoris, a recent Greek immigrant, introduced the diving technique he knew from home. Within a few years, Greek divers and their families had migrated to Tarpon Springs in large numbers, transforming the small town into the sponge capital of the United States.
The Tarpon Springs Sponge Exchange was incorporated in 1908 to organize the storage and sale of sponges, and the industry hit its peak of prosperity in the 1930s. Then in 1939, a disease swept through the local sponge beds, devastating the crop of healthy sponges for several years. The industry never fully recovered to its former scale, though Tarpon Springs still has a working sponge dock and a strong Greek-American cultural identity tied to the trade.
The Physical Toll on Divers
Sponge diving has always been dangerous. The most obvious risks of freediving are drowning and shallow-water blackout, where a diver loses consciousness near the surface as oxygen runs out. But sponge divers also face a less intuitive threat: a form of decompression sickness that was long thought to affect only scuba divers.
Repetitive breath-hold diving can cause nitrogen to accumulate in the body’s tissues. Normally, a single freedive doesn’t last long enough for this to matter. But sponge divers make dozens of deep dives in a single working day, with only brief rest between them. Over hours of this pattern, enough dissolved nitrogen can build up to form bubbles during ascent, particularly in the brain. This condition is called Taravana syndrome, and its symptoms are predominantly neurological: stroke-like episodes, confusion, agitation, and cognitive impairment that can range from subtle to severe. Some effects may go unnoticed at first but accumulate over years, affecting long-term brain health.
When standard diving suits with air hoses arrived on Kalymnos in the 19th century, they allowed divers to stay deeper for longer, dramatically increasing the harvest. They also introduced classical decompression sickness (“the bends”) on a devastating scale, since early suit divers had no understanding of decompression stops. The death and paralysis rates were staggering, and many Kalymnian families lost fathers and sons to the new technology that was supposed to make their work easier.
Why the Trade Declined
Several forces converged to shrink the sponge diving industry. Synthetic sponges, introduced in the mid-20th century, undercut the market for natural sponges. Overharvesting reduced sponge populations in traditional beds. And disease dealt repeated blows. In the Mediterranean, mass mortality events have killed 70 to 95% of sponge populations in affected areas, with warming water temperatures making outbreaks worse. When mortality rates are that high, or when overfishing has already thinned the population, recovery is uncertain. Researchers studying Mediterranean die-offs have predicted the potential extinction of some of the hardest-hit populations.
All five Mediterranean commercial bath sponge species are now considered under threat from the combined pressure of overharvesting and spreading disease. The result is that sponge diving as a full-time occupation supports far fewer people than it once did, though small-scale harvesting continues in Greece, Florida, and parts of North Africa.