NO retaining water is not being well-hydrated!!

Being well-hydrated means that you're peeing fairly frequently and peeing clear. If you're peeing dark in the morning, you're either not well-hydrated or you've eaten something affecting your urine color.

Drink 8 glasses of water-based (non-caffienated, non-alcoholic) beverages a day ... and drink one 750 ml bottle of water and/or sports drink every 1 to 1.5 hours on your ride, and you should be in pretty good shape.