For generations, Somalis made a living fishing their rich waters. Families of fishermen plied the coastline with traditional dhows and motorised skiffs.
Under the decades-long rule of Siad Barre, the country's former president, a maritime force protected the fisheries for domestic use. This force also sold lucrative licences to foreign companies that wanted to join in, the naval historian Gary Weir explained in the article, Fish, Family and Profit: Piracy in the Horn of Africa, published in the US Naval War College Review.
That government collapsed in 1991, but the UN peacekeeping force that oversaw the country for the next four years dispatched a naval unit to continue to monitor the waters.
In 1995 they withdrew. Foreign firms began swooping into the country's waters with little fear of repercussion.
At first the Somali "pirates" consisted of fishermen who boarded the foreign vessels to accuse them of trespassing and demand compensation.
They called themselves a coastguard and were often organised by local clan militias. The clans also began requiring foreign fishermen to buy expensive licences.
Full-blown piracy emerged in the early 2000s when the hardest-hit fishermen in central Somalia formed a ring and based themselves in Harardhere. They used their skiffs to zip around the high seas. In the past year, they have added mother ships - presumably hijacked vessels - to spread their reach into the Arabian Sea and Indian Ocean.
Their network of financial backers is believed by many piracy experts to extend worldwide, though the evidence remains hazy.
Pirates are said to launder their ransom earnings through informal channels in Africa and the Middle East, possibly in Nairobi, Kenya or Dubai.
They then deliver it to "investors" as faraway as Canada and the UK, who are often Somali expatriates who reportedly help fund the pirates' crimes and then collect a piece of the profit.
"When people talk about places like Dubai or Nairobi or even London or Toronto, and their involvement in piracy, generally speaking, those are places that can be destinations for the profits of piracy," said Roger Middleton, a piracy expert at the Chatham House think tank in the UK. "It seems that piracy financiers don't have trouble sending money abroad."
Other piracy backers are said to supply intelligence - by tracking which ships are transporting what cargo where - and equipment such as money-counters.
The pirates still, however, carry fishing equipment, say seafarers who have encountered them.
When foreign navies approach for inspection, they drop their weapons into the water and pull out their gear, disguising themselves, or reprising their former role, as fishing folk.