When can I feed watermelon to baby?

My best friend started feeding her son watermelon when he turned 8 months old. She didn't want to introduce the "sweet" and "fun" stuff too early in case baby gets too used to it and becomes too picky. Her intuition was spot on because since baby had a taste of watermelon, it has become become his favourite and he goes a little wild whenever he sees watermelon hahah