Watermelon seems to be hard to find. I've tried several, each having different taste. Either I get watermelon jolly rancher taste that gets old quick, or like I ate the rind of the melon. So far what I found to be a good flavor is D&D Vapor watermelon in a Kayfun with Cellulose cotton. It's the closest I have come to the real thing, but still not perfect. I don't think I will ever find perfect.
Watermelon to me is something I can't use all day. I found out that I love eating watermelon and I love eating raspberries... but not fond of vaping it all day long.