There are many synonyms for the phrase "missed the boat," which essentially means to miss an opportunity or fail to take advantage of a situation. One could say they "dropped the ball," "let the chance slip away," or "missed the mark." Other synonyms include "missed the window," "missed the deadline," or "missed the memo." Essentially, any phrase that emphasizes the idea of a missed chance or opportunity could be used as a synonym for "missed the boat." It's important to remember that missing a chance doesn't necessarily mean all is lost, however, and there may still be other opportunities to come.