You should be hydrating appropriately irrespective of whether you’re on creatine or not. Creatine is an osmolyte and tends to direct the flow of water into the skeletal muscles which does mean that if you’re dehydrated while on creatine, you could be subjecting yourself to an even more dehydrated state. By no means will creatine negatively affect your hydration status, after all it tends to have the opposite effect and can positively impact hydration and endurance by making your muscles hold more water, just make sure you drink enough water.