The word "belly-flopped" means to dive into water or jump from a height onto water, landing on your belly with a splash. The opposite of this term is "gracefully dove," which means to jump or dive into water with an elegant, smooth movement. "Sleekly dived" is another antonym for belly-flopped, implying a clean and streamlined dive into the water. Other antonyms of "belly-flopped" might include "bounded strong" or "entered smoothly," emphasizing the importance of technique and skill in diving or jumping. Whatever the opposite of "belly-flopped" might be, it signifies a smoother, more controlled, and less painful attempt at entering the water.