Watermelon is one of the five skins released under one part of the Summer offer. It could be individually purchased with game coins in July 2016.
Watermelon could be purchased in the Skins Shop under the ‘Summer’ tab for 690 coins. This skin was available for a limited time and may not be available for purchase in the future.
Details of this skin can vary depending on location, platform or time.
Note: The part of the Summer offer with the Watermelon skin was released again for a limited time in mid June 2019. The price for Watermelon remained the same at 690 coins.