It surely is! Tried one in Starbucks at Tokyo Big Sight and it was so refreshing.The melon drink from Starbucks mentioned at the end is probably the Watermelon Frappucino (link to an article that talks about+taste tests it) which does sound pretty good.
Now now, let's not rule out uuhh...uhhh...mmm yeah I can see it being him.I swear if this turns out to actually be Schwarz