Place a cutting board on a stable surface and use a chef's knife to cut fresh watermelon into 1-inch cubes. Transfer the diced watermelon into a large mixing bowl.
Repeat the process with the pineapple, cutting into similar-sized pieces, and add to the same bowl with the watermelon.
Toss the combined diced fruits gently with a spoon until evenly mixed, ensuring the juices begin to blend for a colorful presentation.
Optional: Cover the bowl with plastic wrap and refrigerate for 10-15 minutes to enhance flavor and chill the salad before serving.
Serve the fruit salad in individual bowls or a large serving dish, with visible juicy chunks and bright colors, ready to enjoy.