I think there's dehydrated baby melons in a watermelon... You see, a watermelon has seeds in it (also known as baby melons). Without water, a watermelon is just a melon. So a watermelon has to provide water for its baby melons/seeds, so that they'll grow into good watermelons when they're older. If the watermelon doesn't give them any/enough water, then the melons will become either a water-less watermelon, or another fruit/vegetable...
Maybe that'll help? I don't know. But with all due honesty, @Kadrynal
, why do you ask about the melon in watermelon?