That is amazingly beautiful!! That is much more complex than the ones I do!
diannab - just find a pattern you like, tape it to the watermelon and do like the pumpkin carvings - just poke holes in the lines all over and then when you remove the paper, just cut connecting the dots!
I've done watermelon carvings, but I've only made things like a basket with flowers for the handle, a basket with stars and ribbons for the handle, etc. Oh! I also did a pig (y'know, oink oink) for my cousin's open house.