Peel and core the pineapple, then use a sharp knife and cutting board to cut it into bite-sized chunks. Place the pineapple pieces into a large mixing bowl.
Slice the seedless watermelon into similar-sized chunks using the knife. Add the watermelon pieces to the bowl with the pineapple.
Chop the fresh mint leaves finely, releasing their aroma. Sprinkle the chopped mint over the fruit mixture.
Cut the lime in half using a knife, then squeeze the juice directly over the fruit and mint mixture using a lime squeezer or your hand, until about 2 tablespoons of juice are added.
Gently toss all the ingredients together with a spoon or spatula until evenly combined and the fruit is coated with lime juice and mint. Serve immediately in individual bowls for a vibrant and juicy presentation.