That sounds really interesting. You could make a drink with the watermelon/vodka/lime/fennel and rim it with salt [or not]. I bet it would be good. It sounds refreshing as well.
You could even grind fennel and salt into a fine dust and rim it with that.
I agree with richmarshall. First, take a large watermelon, a knife, & a quart of vodka into an empty field, as this can get quite messy. Carve a corkhole into the watermelon. Insert the bottle into the corkhole & wait for the quart to download. Your snack can now be served. Slice pieces of watermelon from the top. Don’t mind if vodka spills out here and there. Eat as much as possible.