Hydration needs differ significantly between endurance athletes and casual exercisers. Endurance athletes often require more fluids due to prolonged exertion, which leads to increased fluid loss through sweating and breath. They should focus on electrolyte replenishment during long events to prevent dehydration and maintain performance. Casual exercisers generally need to hydrate based on their activity level and can often meet their needs through regular water intake. It's vital for all individuals to listen to their body and hydrate appropriately to support overall health and performance.