Antonyms for the word coastlands could be inland, interior, or continental. While coastlands refer to the areas adjacent to the coast, antonyms suggest areas located far away from the coasts or any form of water bodies. Inland refers to areas located deep within the country, away from the oceans, and often characterized by their lack of water bodies. Interior, on the other hand, denotes the areas that are found within a country, away from the coast. Continental, the third antonym, refers to the large land masses of Earth that are not surrounded by oceans, such as Asia or Europe. These antonyms help to capture the variety and diversity in the geography and landscapes of our planet.