The phrase 'up creek' refers to being in a difficult, troublesome or challenging situation. This phrase can have many antonyms or words with opposite meanings. Some of the most significant antonyms for up creek are words like flourishing, successful, prosperous, thriving, booming, and thriving. These words are used to express situations that are the opposite of being stuck or struggling. People use these antonyms to show that everything is going well in their life, and they are not facing any difficulties. Being on top of the world, living the dream, and flying high are other phrases that can be used as antonyms for up creek.