I happen to have a watermelon cider and a german pils dry hopped with Huell Melon on right now. I think the HM would be very complimentary with the watermelon but it just depends on what kind of beer you brew. El Dorado will be significantly more powerful so I would use that if you are going for IPA. If you do the wheat I would go with the huell or you could go with both at a 2:1 hm to el dorado