On April 21st, KRI Nanggala 402, an Indonesia’s diesel-attack submarine was declared lost while underwater. It was declared to be sub-sunk and on eternal patrol after the discovery of its debris. This heartbreaking news sparked a question in my mind, “what is the environmental impact of a sunk ship or submarine that stays underwater?” and in this article I would like to share my findings on the topic.

Before jumping onto the article, to be as respectful as possible towards the deceased, I would like to borrow this short moment to pray for the 53 crew members of KRI Nanggala 402 and wish them rest in peace.

It is estimated that the North Atlantic Ocean alone contains 25% of all potentially polluting wrecks in the world. Seventy-five percent of sunken wrecks can be dated as far as World War II. When properly decommissioned, though, shipwrecks may create artificial environments that support the ocean. However, if these sunken wrecks are not carefully planned, they may have a negative impact on the local environment and become one of the most significant sources of marine pollution. Vehicle collisions can damage coral reefs and prevent them from growing further.

Shipwreck metal structures also age and deteriorate over time, losing a tenth of a millimeter of thickness per year. As various contents are often carried out inside this shipwreck, this process poses the possibility of leaking their contents into the ocean due to corrosion. Oil is one of the cargoes carried by ships. Some processes cause the oil to ‘disappear' in its original shape, but just because it isn't apparent on the water surface doesn't mean it's gone or harmless to the setting. Even though shipwrecks usually leak only a small amount of oil, they can cause significant damage by smothering beaches and killing seabirds.

However, oil isn't the only danger to marine biodiversity. Toxins are another dangerous content threatening the ocean sustainability. The majority of toxins are proteins that can cause disease when they come into contact with or are absorbed by body tissues. Toxins vary greatly in their severity, ranging from mild and acute to directly fatal. As a result, they pose a health risk to both animals and humans.Toxins build up in food systems. When larger fish consume infected smaller fish, they all become poisoned. These fish can then be consumed by other fish, mammals, birds, or humans, passing on the poison.

Though, it is worth noting that with so many wrecks in the sea, the positive environmental effect of shipwrecks has become apparent. Wrecks off the coast of Hawaii, for example, have provided opportunities for the islands' ecological development. These wrecks can benefit the ecosystem by providing a suitable habitat for a variety of marine plants and animals, as well as improving water quality.