"Underwater" refers to the state of being beneath the surface of a body of water, such as an ocean, lake, or river. This environment is characterized by unique physical properties, including pressure, temperature variations, and light absorption. Many organisms, like fish and marine mammals, thrive in this habitat, adapting to its conditions. Exploration of underwater environments is conducted through various means, including scuba diving and submersibles. Technologies like sonar and underwater cameras help scientists study ecosystems, such as coral reefs and deep-sea trenches. Notable underwater locations include the Great Barrier Reef and the Mariana Trench, which are rich in biodiversity and geological features.