The watermelon contains about 92% of water and only 5% of sugar. That’s why its consumption causes increased micturition.
Some might think this is annoying, but just think that this way it cleans the blood from all sorts of poisons and the kidneys from salts and small stones!
Furthermore, the large amount of water is the main reason why we should never consume it right after lunch or dinner, since it has negative effects on digestion.
You should prefer it raw and any other time.