The antonyms for the phrase "throw overboard" include "keep," "retain," "hold onto," "preserve," and "save." These antonyms suggest the opposite of throwing something away or getting rid of it. They denote an action that involves keeping something with oneself, protecting or preserving it. These antonyms can be used in various contexts, from physical objects to people, ideas, or emotions. For example, if you are considering throwing away a book, its antonym might be to keep it, cherish it, and preserve it for future reading. Similarly, the antonym for throwing someone overboard would be to save or rescue them.