Gently rub your watermelon with a clean, wet washcloth to remove any dirt or grime.
Rinse your cantaloupe in lukewarm running water. Leave on counter to dry.
Slice your watermelon lengthwise with a carving knife through the middle and to the center of the fruit as viewed from above, cutting in the direction away from your arms and body, in a straight line through the fruit.
Make a handle so the watermelon rind resembles a basket, by cutting away the top quarters. When viewed from the side, cut the melon from the 9 o'clock position lengthwise to almost the center with a long carving knife, then turn the knife upward and cut in the direction away from you to the 12 o'clock position. Choose a handle thickness for the rind (1 1/2 inches is attractive), then cut straight down from the 12 o'clock position to the center of the fruit, turn the knife toward the opposite end and cut toward the 3 o'clock position.
Pull away the two cut quarters and hollow out beneath the curved rind handle by cutting away from your hands and arms, setting aside the chunks of watermelon.
Use a smaller paring knife to carve all of the fruit from inside the watermelon in 2-inch chunks, but leave the watermelon rind intact, as this will be the centerpiece to house all of your attractively presented fruit.
Wipe down the inside of the carved watermelon bowl that you plan to use as your centerpiece. Carve the edge of the length of the bowl into jagged edges (such as you would see for a broken Easter egg decoration). You may leave the watermelon centerpiece as-is; carving the edges is optional. Refrigerate the hollowed watermelon rind.
Use the knife to carve the cantaloupe in half. Scoop all the seeds from the cantaloupe (they have a bitter taste) and dispose in a trash bag.
Remove all of the fruit from the cantaloupe, ensuring that fruit is sliced in increments of at least 2 inches for cutting into shapes later. Place fruit from sliced watermelon and cantaloupe onto a flat surface, such as a cookie sheet or cutting board.
Use cookie cutters to cut and carve various shapes out of your watermelon and cantaloupe. Cookie cutters are available in a variety of themes, and make excellent fruit carvers for holiday parties and special occasions. Stars are particularly attractive when presented inside the carved watermelon bowl.