Iron Ocean

The Iron Ocean (アイアンオーシャン, Aian Ōshan, also known as 鉄海, Tekkai) is a mutated expanse of water in Black★★Rock Shooter DAWN FALL. It is a source of energy for the Unmanned Forces. The Iron Ocean was the main setting for the episode Crossing Iron Oceans.

History
When Artemis chose to attack humanity, the nanomachine known as Arche went out of control and contaminated the sea before being spread into the earth. By the present time, the Arche in the sea gave rise to the Iron Ocean. Humans who are captured by the Unmanned Forces are taken here, where they are fired into the sea by a Gigantes-type Titan. This draws out energy for the Unmanned Forces and causes new machines to emerge from the ocean.

According to a map seen in Black falls down a hole, the Iron Ocean surrounds the entire coastline of the United States, and extends nearly as far out as the South Pacific Ocean. The same map also notes the Caribbean Islands (listed as the Former Caribbean), part of southeast Mexico, and the land directly connecting the North and South American continents as having been eroded due to the toxicity of the Iron Ocean.

Despite the inherent danger the Iron Ocean presents to humans, in Crossing Iron Oceans, it was shown that Isana would swim in the ocean rather often, and even drag in Monica Kaburagi with her. This revealed that the Iron Ocean is not immediately harmful to humans, but prolonged and repeated exposure would cause one's body to be contaminated with Arche that crystallizes within them.