I have at least one other recipe, but can't seem to find it right this minute. Here is a recipe for Watermelon-Peach Wine. This is not exactly what you asked for, but should nonetheless serve you nicely. The peach helps, as watermelon alone lacks body and can make a disappointing wine.
Extract the juice from watermelon and peaches, saving pulp. Boil pulp in one quart water for 1/2 hour then strain and add water to extracted juice. Allow to cool to lukewarm then add water to total one gallon and all other ingredients except yeast to primary fermentation vessel. Cover well with cloth and add yeast after 24 hours. Stir daily for 1 week and strain off raisins. Let stand additional 24 hours and rack. Pour into secondary fermentation vessel, fit fermentation trap, and set aside for 4 weeks. Rack and set aside another 4 weeks, then rack again. Allow to clear, then rack final time and bottle. Allow 6 months before tasting, but improves with age
My thanks to Pamela Malnar for the request.