The Sierra Madre was grounded on the Second Thomas Shoal by the Philippines authorities in the 1990s — a detachment of marines is stationed on the rusting hulk.

Tomas Etzler is a journalist and filmmaker who has covered everything from the war in Afghanistan to the 2011 Japanese tsunami during a career that has spanned nearly three decades. His most recent assignment took him to one of the most remote destinations in the South China Sea to witness firsthand a unique international dispute.

Spratly Islands, South China Sea At first glimpse, it looks like a ghost ship anchored in the middle of the ocean, but this rusting, rat-infested former U.S. Navy warship is actually at the frontlines of an increasingly tense dispute between the Philippines and China. Deliberately grounded on a tiny reef in the South China Sea, part of an island chain claimed by the two Asian countries, the Sierra Madre is now the unlikely base for a detachment of Filipino marines who stand guard over the atoll, scanning the turquoise waters for Chinese ships. Just reaching this unusual landmark, located 105 nautical miles (194 kilometers) from Palawan province in the western Philippines, is a nerve-jangling experience. We approached the submerged reef in our aging wooden fishing boat at top speed — 11 knots per hour. From the north, a modern Chinese coast guard ship was closing in at least twice as fast with the intention of blocking our path. A second Chinese vessel quickly approached from the south with the same idea. "We are prepared here just in case China attacks us. The school was assigned as an evacuation center. I am nervous because it might happen. What will happen to us?" — Jacqueline Morales, Pag-asa resident But they didn't make it. After several tension-filled minutes, we entered the shoal, which was too shallow for the larger Chinese boats to follow. Some of the fishermen on our boat prayed in relief – it doesn't always happen this way. It's probably fair to say not many people have heard of the Second Thomas Shoal, which is known as Ayungin in the Philippines and Ren'ai Jiao in China. This teardrop-shaped reef is part of the Spratly Islands, a mostly uninhabited archipelago midway between the Philippines and Vietnam, claimed entirely by China and in its various parts by the Philippines, Brunei, Malaysia, Taiwan and Vietnam. To complicate matters, the conflict has sucked in the United States, which has a mutual defense agreement with the Philippines and is urging a peaceful resolution. It has also prompted closer security ties between the Philippines and Japan, which is itself at loggerheads with China over islands in the East China Sea. While some of these disputes focus on little more than clusters of uninhabited rock, the outcome of this territorial wrangling has the potential to sway the balance of power across the region. The value of some of these territories actually lies under the seabed with pockets of natural gas and oil — as we've seen recently with the deployment of oil exploration rigs by China off the Paracel Islands — another disputed chain in the South China Sea.

The start of a difficult journey Getting to the Second Thomas Shoal took months of negotiations with Philippine authorities – because of logistical and security concerns – and then seven days traveling by boat. I started the odyssey in April this year in Puerto Princesa, the capital of Palawan province. I was traveling with Eugenio Bito-Onon Jr., the mayor of Kalayaan, the smallest and one of the poorest municipalities in the Philippines. It consists of 10 tiny islets and reefs situated at the northern tip of the Spratlys. We were headed for Pag-asa first, the only island in the area with a civilian population. It was also the staging point for reaching the Sierra Madre. Usually based in Puerto Princesa, Bito-Onon only manages to travel to Pag-asa once a year. We stopped at a few smaller islands on our journey, each home to small detachments of marines from the Philippines — the last line of defense against foreign encroachment. The journey: Journalist Tomas Etzler makes the long journey to Pag-asa in the Spratly Islands territory claimed by the Philippines and China. Some of those marines admitted it was a lonely mission but said they were proud to serve in such a remote outpost in defense of Philippines territory. Others claimed it was "fun and exciting" to monitor foreign ships, mostly Chinese, moving into their waters. At the end of the third day of our journey, we finally arrived in Pag-asa, the second-largest island in the Spratlys. Previously a military base, the Philippines government encouraged civilians to move here in 2002. More than 12 years on, and 120 people now live alongside the small units of Philippines air force, navy and marines still stationed here. Jacqueline Morales, 28, moved to the island from Palawan with her husband and two children. She wanted to serve her country and heard that Pag-asa was in desperate need of teachers. While residents' living costs are partially subsidized by the central government, she admitted the "China factor" is a real worry. "It feels like part of a movie set for a sequel to 'Mad Max' or 'Waterworld.' The bridge tower is so rusty it looks like it could collapse at any moment, while the hull is pockmarked with numerous rusting holes." "I watch television. We know the Chinese are interested in the island," she said. "We are prepared here just in case China attacks us. The school was assigned as an evacuation center. I am nervous because it might happen. What will happen to us?"

Preparing for Chinese blockade As we planned the final part of our journey — to the Sierra Madre itself — we discussed the possibility of encountering Chinese coast guard ships with the crew of the modest fishing boat we hired for this leg of the trip. We were told the Chinese have stopped or tried to stop boats entering the shoal. We agreed the strategy would be that unless the captain felt his boat was in danger of being rammed — not uncommon in many of the territorial disputes in this region — he would try to outmaneuver the Chinese to reach his destination. [+] Click to enlarge Chinese coast guard ships loom on the horizon just beyond the shoal, which is part of the Spratly Islands -- territory claimed by both the Philippines and China. The Sierra Madre was built by the United States in 1944 to serve in the Pacific as a transport ship during World War II. It changed hands twice after the war. First it was transferred to the South Vietnamese navy during the Vietnam War, then to the Philippines after the fall of Saigon, now known as Ho Chi Minh City. In 1999, the Philippines purposely grounded the Sierra Madre at the Second Thomas Shoal. The secretary of defense at the time, Orlando Sanchez Mercado, claimed it was in reaction to China's decision in 1994 to take control of Mischief Reef, just 13 nautical miles northwest from Second Thomas Shoal. "We were forced, and we had no recourse but to look for means by which we can retain our presence," he explained. "And during our watch, we decided that the best we could do was to beach this particular ship and keep our troops there. They have been there for all this time." Manila claims the disputed locations are within its 200-nautical mile exclusive economic zone. China, which refers to the Spratlys as the Nansha Islands, maintains it was the first to discover and exercise sovereign jurisdiction over the islands. China even suggests that its right to them was cited in international documents such as the Potsdam Proclamation, which defined the terms for Japan's surrender after it occupied much of the region during World War II. The islands are part of a huge swath of the South China Sea and fall within what Beijing calls its "nine-dotted line," a U-shaped line marking off territory that China claims sovereignty over. Wreck patrol: A detachment of Philippines marines are stationed on the rusting Sierra Madre, a deterrent against Chinese encroachment. Most boats approaching the Second Thomas Shoal come from Palawan, from the southeast. We came from the northwest, which the Chinese patrol boats would not anticipate, our skipper reasoned. That's why our boat surprised and eluded them. From a distance, the Sierra Madre looks like any other big ship. It's only when you get closer you realize something isn't right. The sun-scorched hulk towering above the shimmering blue waters of the shoal looks like it could be part of a movie set for the sequel to a postapocalyptic epic such as "Mad Max" or "Waterworld." The bridge tower is so rusty it looks like it could collapse at any moment, while the hull is pockmarked with large, rusting holes. [+] Click to enlarge A Philippines marine with a makeshift spear fishes for dinner in the shadow of the Sierra Madre. In the surrounding waters, I spotted a few men swimming with snorkels as we approached. They were some of the few marines stationed here out fishing. Both Chinese ships that had initially given chase were now watching from outside of the shoal just several hundred yards away. It was an unreal and absurd scene. After climbing on deck via a worryingly makeshift ladder, we were greeted by Lt. Earl Pama, the commanding officer. The 29-year-old marine's unit had been here since March 30. As with other islands in the area, the marines are rotated in and out every three months. It's not an easy deployment; Pama's unit got to Sierra Madre only on the second attempt. Their first approach was blocked by Chinese coast guard ships.

Chinese ships like predatory sharks By late afternoon on our first day there, three more Chinese ships arrived in the vicinity. The Sierra Madre was now surrounded by five vessels, which were slowly circling the shoal like predatory sharks. As I peered through my binoculars, I saw some of the Chinese sailors were looking right back at the ship taking pictures using cameras with long lenses. [+] Click to enlarge A lone marine surveys the brilliant blue waters of the atoll from the deck of the rusting hulk. As the sun disappeared from the horizon and the light faded, I was introduced to more of the Sierra Madre's inhabitants: huge cockroaches and rats. "I estimate there are five to six hundred rats and a million cockroaches," one of my marine hosts said with a laugh. I was offered a cabin — a damp, mosquito-infested space complete with filthy mattress in the middle — but the presence of our nocturnal guests prompted me to use it store my gear while I spent the night on the roof of our fishing boat. The marines endure tough conditions here. They face a merciless sun and searing temperatures. During rain showers or typhoons, the radio room, their only contact with superiors in Palawan, is the only one on the ship that doesn't leak. The soldiers are cut off from the outside world most of the time. "I estimate there are five to six hundred rats and a million cockroaches." — Hilbert Bigania, Philippines marine "Our life here is hard sometimes because we are far from our families," Hilbert Bigania, a 30-year-old sergeant, said. "We can't communicate with them, and we're in the middle of the ocean. That's our everyday life here. We can't do anything." It can also be a struggle just to survive. The marines claim that in 2012, the Chinese ships became more aggressive and started to harass Philippine navy vessels bringing in troops for rotation and supplies. "What they do is they block the provisions that would be delivered to us, so that we don't have food to eat and we don't have supplies or even water," said Pama. Fearing an open conflict with the Chinese, the Philippine navy began to use airdrops or civilian fishing vessels to bring in supplies. On my second day on the Sierra Madre, two small navy planes dropped two loads of supplies. One landed on the ship, the second in the water. The Philippine planes appeared to be shadowed by other aircraft — Chinese spy planes, the marines claimed. [+] Click to enlarge The detachment of marines spend three months stationed on the Sierra Madre, enduring extremely difficult conditions. The small containers held basic food supplies, soft drinks, flip-flops and towels. But what cheered the marines most were letters of support from schoolchildren as well as boxes from a fast-food chain filled with fried chicken, rice and French fries. It was a rare feast, as there are only one or two drops like this during each deployment. The bulk of their diet consists of fish they've had to catch. Using handmade spear guns or makeshift rods, they fish twice a day. The waters surrounding the boat are as shallow as 5 feet (1.5 meters) and full of marine life. The soldiers move around the shoal on an improvised rubber raft and use strips of wood with rubber straps as flippers to propel themselves around the water. The catch is then dried and grilled on the deck of the ship. Fishing also helps them to kill time; there's not much to do on the ship. Even walking on the deck is dangerous. The Sierra Madre is severely weathered and riddled with holes. When not fishing, the marines monitor their Chinese shadows, clean their weapons, exercise using broken off metal parts from the ship as weights or simply relax in their hammocks, listening to Filipino pop music. [+] Click to enlarge The Chinese are waiting patiently for the Sierra Madre to break up before they move in. But most of the time it's a seemingly endless waiting game for them, wondering if their territorial rivals circling the ship will make a move. The Chinese have no reason to invade the shoal. They've become increasingly assertive in their territorial claims across the South China Sea in recent years, but they seem in no rush. All they need is patience — it's only a matter of time before the Sierra Madre falls apart and its residents have to leave. The Chinese ships can then move in without a shot being fired. Earlier this year, the Philippines filed a case with the United Nations over China's conduct in the South China Sea, including the encirclement of the Second Thomas Shoal. China says it will not accept international arbitration, saying the only way to resolve the dispute is through bilateral negotiations. "Regardless of how the Philippines packages its lawsuit, the direct cause of the dispute between China and the Philippines is the Philippines' illegal occupation of part of the islands in the South China Sea," Foreign Ministry spokesman Hong Lei said in a statement in March. The government officials I spoke with in Manila said that even if the ruling, which is expected early next year, goes against China, it won't change much. There are no mechanisms to enforce the ruling. The standoff between the two countries will likely continue for years.