For nearly two years now, the Yemen Navy has had an arrangement with a British security company, to provide paid (up to $55,000) escorts for ships traversing the pirate infested Gulf of Aden. This is one the busiest shipping lanes in the world (with nearly ten percent of all traffic). Each month, 1500-1600 ships pass the northern coast of Somalia. For the last two years, 3-4 of those ships have been seized (and up to ten, or more, attacked) by pirates each month. That's one ship out of every 400-500. But with the pirates getting more and more ransom money for each ship, the number of pirate groups operating in the Gulf of Aden is increasing.
Most merchant ships are wary of pirate operations, and put on extra lookouts, and often transit the 1,500 kilometer long Gulf of Aden at high speed (even though this costs them thousands of dollars in additional fuel). The pirates seek the slower moving, apparently unwary, ships, and go after them before they can speed up enough to get away. For the pirates, business is booming, and ransoms are going up. Pirates are now demanding $3 million or more per ship, and are liable to get it for the much larger tankers and bulk carriers they are now seizing.
The larger, and more valuable, ships find that the additional security services (which include armed security guards on the ship while moving through the straits) worth the expense. Each month, 30-40 ships pay for this service, with the British security firm handling marketing and scheduling, and splitting the $55,000 (or more) fee with the Yemeni Navy. It's unclear if the Yemeni government was aware of this arrangement, as such freelancing by government agencies in Yemen is not unknown. Four of the ships being escorted were attacked anyway, but the attackers were driven off. Many more attacks were avoided because of the presence of the Yemeni patrol boat.