There is a morbid poetry in the photojournalism of Juan Medina; an empathetic, and unnervingly aesthetic look at death and the struggle for life. As a Reuters photographer based in the Canary Islands, Medina's day-to-day photo calls rarely make headline news. But for the past seven years, he has been documenting one of the world's busiest and deadliest illegal immigration routes in which up to 1000 immigrants a week leave Africa's west coast hoping to reach the Canary Islands, and EU territory. Hundreds are detained every week in Spanish centres. Dozens more drown in unseaworthy, overloaded boats.

Medina's images tell of a man who has been following this story for years. His most striking photographs avoid the obvious dramatic moments - the pile of dead, anonymous bodies on an otherwise pristine beach - that have become symbolic of this constantly repeated tragedy. Instead, his impact lies in looking at the details, at what happens when the world of the illegal immigrant collides with the world of the coast guard, the Red Cross worker, or the tourist. In one image, a crowd of tourists camped on one of the Islands' famous beaches stares, motionless, at a pair of dead bodies. In another image, a group of tourists - ageing and naked except for swimming trunks - carries the body of an immigrant on a stretcher. He photographs a family cowering on the boardwalk as a pair of disoriented recent arrivals, still dripping wet, stumble along the pavement. One of his most disturbing images shows the hands of a cemetery worker hammering a plaque into place on a concrete coffin. The plaque simply reads "Immigrant No. 3". It is true, some of Medina's images are little more than piles of dead bodies on the Canary Islands' rocky shore. But the photographs that really define his style are more biting confrontations that seem to ask the viewer "what would you do in this situation?" and wonder, crucially, what role we might unwittingly play in this mass exodus.

Medina is a commercial photographer, but he approaches this project with an altogether different compulsion: it is a bold emotional reaction to what he describes as "an inhumane act." "Keep in mind that when the Berlin Wall fell in Germany," he explains through a translator, "the European governments were happy. But then after that, all they've been doing is building more walls, or using the sea itself as barricade." In contrast to the daily duties of a wire photographer - sent by the agency to cover a singular event - Cruel Sea is an ongoing process of waiting, every night, to hear news from one of his aid agency or coast guard contacts that a boat is landing. It is a process that produces a body of work often more introspective than shocking. Medina looks closely at what happens when the immigrants are caught and "processed": who handles them? (military or aid agency?) Where are they taken? (mainland Spain or a holding centre in West Africa?) How are they treated? (like criminals, or like victims?) Aware that both the emergency services and the journalists covering their work are on the same side, Medina explains: "I feel like I have a lot of responsibility to show this as much as I possibly can…I think the best way to do it is to document every day, because then every day there will be new pictures and new things going on. They are constantly changing."

The route from Mauritania's coast to the Canary Islands is a relatively new one for illegal African migration. The traditional passage has always been to cross the narrow Straits of Gibraltar between Tangier and the coastal cities of southern Spain, but as security steadily increases along that border, and following the tragic death of 11 migrants who stormed the security fence surrounding Ceuta and Melilla last autumn, much of Africa's illegal traffic has moved to the Mauritanian route. I investigated the crossing via Tangiers in January of 2004 for the documentary I See The Stars At Noon. Following Abdelfattah, a Moroccan determined to find a way to illegally enter Europe, I wanted to understand what would compel someone to risk his life for an uncertain, and often unrealistic, future. I found in Morocco an extremely compelling mythology based around the clandestines, the illegal immigrants, and what they found when they arrived in Europe. Rumours of plentiful jobs and friends with valuable contacts are fuelled by those successful clandestines who return to Morocco in the summer with stories, often untrue, of the success they have found. I was told that many who made it into Europe, too ashamed to admit they were homeless and unemployed, would borrow money to buy new clothes, and sometimes even cars, to prove to their families and friends back home that it was worth it. The result is a dangerous and often deadly cycle the few are willing to openly debate.

When, in mid 2003, I visited Tarfiyyah, a fishing village on Morocco's south-western coast and Africa's closest point to the Canary Islands, locals were already talking about hopeful migrants paying fishermen, or buying their boats, to attempt the crossing. Since then, the traffic has been moving steadily further south as security struggles to keep up with the increasing number of illegal immigrants. Medina explained of the Mauritanian route, "It's always in a flux because it keeps changing, in terms of where you depart from. Before it was Western Sahara, then Mauritania, and then Senegal, so each time it's [further and further south]."

With each move, the journey becomes longer, and more dangerous. Many of Medina's images illustrate the number of deadly obstacles plaguing the trip: bodies strewn against the sharp volcanic rocks that define the Canary Islands' coastline and migrants struggling to escape their capsized and overcrowded boats. In the northern Tangiers route, most clandestines are very aware of these dangers. Abdelfattah called the inflatable Zodiac rafts that often sink in the Straits "boats of death," and chose instead to sneak on to a cargo ship for the crossing. His challenge, and one that distinguishes the more established Tangiers route from the newer Mauritanian route, was not so much how to survive the crossing, but what to do once he arrived. For those lucky enough to find it, there is a network of people willing to help the newly arrived clandestine, offering illegal jobs, transportation, or contacts. The Tangiers route is so well established it has acquired its own folklore and vocabulary on the streets of Morocco, with young Moroccan men (the clandestines are almost always men) talking about the illegal emigration as though they were discussing their plans for the weekend. The Mauritanian route, on the other hand, is still something of a deadly adventure that has caught both West African and European governments by surprise. Despite this difference, the goal of Abdelfattah was the same as that of the thousands of anonymous - living and dead - that Medina has photographed over the years: to reach EU territory, and to immediately disappear into the system, one way or another.

Cruel Sea by Juan Medina is exhibited at the HOST Gallery, Honduras Street, London EC1 until the 7th May. Visit HOST Gallery's website www.hostgallery.co.uk

for more information. Saeed Taji Farouky is a filmmaker, writer, photographer and musician. To purchase a copy of his film, I See The Stars At Noon or to arrange a screening visit his website www.touristwithatypewriter.com