The "Underwater World" refers to the vast and diverse ecosystems found beneath the ocean's surface. This environment is home to a wide variety of marine life, including fish, coral reefs, and sea mammals like dolphins and whales. These ecosystems play a crucial role in maintaining the planet's health by regulating climate and supporting biodiversity. Exploring the underwater world can be done through activities like scuba diving and snorkeling, which allow people to observe marine life up close. Additionally, advancements in technology, such as submersibles and underwater cameras, have made it easier to study and understand these unique habitats and their inhabitants.