As a kid, I remember having watermelon slices in the summer and what a treat it was! This was at the time when all watermelon had seeds so, of course, as we ate the fruit, we had to have seed spitting contests. As it turns out, we should have been eating those seeds too! Just like other edible seeds, there are many benefits to them.
http://www.livestrong.com/article/24243-health-benefits-watermelon-seeds/