Image copyright AP

A small multinational fleet patrols the Mediterranean, hoping to intercept and rescue the thousands of refugees trying to reach the coast of Italy. It can be a thankless task.

Clinging to the safety bar of the top bunk in the hot and airless cabin, I decide I want to die. For 24 hours now the sea has boiled beneath us, catapulting us upwards on the swell and then crashing back down, the 5m (15ft) waves squeezed and squashed under the ship's hull with the juddering force of a pneumatic drill.

The metallic stench of bile and acrid engine fuel is choking me - I've been sick so many times now that I am shaking. And there's no getting off - we're on board an Icelandic coastguard vessel in the middle of the Mediterranean, part of a mission run by the EU's border agency, Frontex, to intercept a cargo ship which is suspected of having migrants hidden in its hold. I try to imagine them, three to five hundred of them perhaps, crammed into the bowels of the boat with no space to lie down, the waves smashing them against the hull and scattering them like skittles.

"I never thought I'd see anything like it," crew member Andri Johnson had told me when we'd sat together on deck near the port. Last month Andri was part of the rescue team which saved hundreds of migrants on a rusty decommissioned cargo ship which had been abandoned by its crew off the Italian coast. He spoke hesitantly, not because of a lack of fluency in English, but because he clearly didn't welcome revisiting dark memories. His young, moon-shaped face gave him a curious look of purity and innocence.

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"When I boarded the ship and saw the dirt, the lack of hygiene and the women and children so dehydrated who'd had no food and water for days... it was just so terrible and so moving. You know I have such a good life and to see those people struggling..." He trailed off and looked down at the deck. "We can't give up you know," he said firmly. "These people need our help."

The problem is too many people need Frontex's help. More than 19,000 migrants have arrived on Italy's shores since last November. Frontex which doesn't have any operational equipment of its own, relies on EU or Schengen member states (like Iceland) to lend it the planes, ships and helicopters it needs for operations. It currently has a handful of resources to cover the huge Mediterranean sea.

On the ship's bridge, Capt Einar Valsson shows me the course he is plotting to intercept the suspicious cargo ship. I'm alarmed when I realise it's over 100 miles out to sea. The captain shrugs.

"When the distress call comes, we have to answer that call. We come from Iceland," he reminds me. "A small country of 300,000 people. One life is very important for us - we can't just leave people in the Mediterranean."

Media playback is unsupported on your device Media caption The BBC's Emma Jane Kirby joined a Frontex crew patrolling in the Mediterranean

But people are being left, no matter how many rules Frontex is bending. Aid agencies say that last week's tragedy, in which more than 300 migrants drowned off the coast of Lampedusa, shows how woefully inadequate the mission is. When the emergency calls for help sounded, both of Frontex's large vessels, including the Icelandic one I'd been aboard, were in port and too far away to help. Twenty nine migrants who were rescued by a small vessel died of hypothermia on the way back to shore. Doctors on the scene claimed if they had been picked up by a big naval or coastguard ship, they probably would have survived. Italy decided to end its Mare Nostrum mission after its EU partners refused to share the high costs of running the operation. Ironically it's those same reluctant EU partners who are now being relied on to offer handouts to Frontex.

Image copyright Getty Images Image caption More than 580 people - mostly from Syria - disembark in Italy after being rescued by Frontex last December

After 29 hours of misery, Captain Valsson finally steers us into the safety of Pozzallo port. It's been a frustrating mission for him - by the time he'd caught up with the suspicious cargo ship, it had moved to international waters meaning his crew did not have the right to board and inspect it. No-one can now be sure if it was hiding migrants in its hold - the ship has plotted a new course towards the Canary Islands.

"This," he says, gesturing towards the water, "is what we call a pig of a sea. Tomorrow, it will be worse."

Tomorrow, right now, more desperate people will be stepping into dinghies, inflatable rubber boats, handing over money for a place in the engine room of a rusted cargo ship. I understand a little now of how pitiful their journeys will be. I daren't guess as to how they will end.

Image copyright Getty Images Image caption The Icelandic coastguard vessel Tyr, off the coast of Sicily

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