In the lagoon of Chuuk, a small island in Micronesia, more than 65 shipwrecks and 250 aircraft remain submerged, untouched by salvage efforts. These wrecks were sunk during two major bombing raids in February 1944, as part of World War II. According to a 2016 study published in Frontiers in Marine Science by Ian D. MacLeod, a researcher from the Western Australian Maritime Museum, the wrecks still contain fuel that has been trapped for over 80 years. The steel hulls have been slowly rusting, with corrosion advancing about 0.1 mm per year, though this rate varies depending on factors like depth, salinity, and water temperature. MacLeod previously found that the wrecks in Chuuk corrode 26 to 30% slower than those in open sea at the same depth. Over 82 years, this slower rate has led to an estimated loss of about 8 mm of steel. The fuel remaining inside the wrecks is a major concern, with estimates ranging from 22 million to over 100 million liters of oil and diesel. The Japan Mine Action Service (JMAS), a program funded by the Japanese Ministry of Foreign Affairs, has identified 15 priority wrecks for cleanup. Efforts so far have recovered only a small fraction of the estimated fuel, with 60,000 liters removed since 2017. One of the most significant wrecks is the Kiyosumi Maru, an 8,614-ton ship resting at 30 meters depth. It has a large torpedo breach and is estimated to contain more than 60,000 liters of oil. Experts warn that a strong storm could damage the wreck and release millions of liters of oil into the lagoon. In 2007, a leak from the Hōyō Maru caused a 7 cm layer of oil to coat the shoreline, highlighting the risks. In 2011, the president of Micronesia called these wrecks "environmental time bombs" during a United Nations General Assembly speech, prompting the JMAS to begin its cleanup efforts in 2017. On September 11, 2025, a leak was detected from the Rio de Janeiro Maru, a wreck from 1944. The oil sheen spread toward nearby islands, prompting warnings about toxic fumes and contaminated water. The governor of Chuuk, Alexander R. Narruhn, declared an emergency, and the Micronesian president, Wesley Simina, sought international help at the 80th United Nations General Assembly. The leak was eventually contained using a collection tank placed on the wreck. While the situation has improved, the threat remains. The wrecks are not only an environmental issue but also a major tourist attraction for Chuuk. The exact number of wrecks varies between sources, with estimates ranging from 44 to 65. Beyond Chuuk, the Secretariat of the Pacific Regional Environment Programme (SPREP) reported more than 1,200 potentially polluting wrecks in the Pacific in 2022. As the steel continues to corrode, the risk of oil leaks remains a pressing challenge for the region.