When running a marathon, you should have access to water at the aid stations that are set up throughout the racecourse. However, some marathoners choose to carry their own water in a handheld bottle or hydration belt. Some benefits of carrying your own fluids include having easy and spill-free access to water when you need it and avoiding the crowds and chaos at aid stations. On the other hand, some marathoners say they feel weighed down when carrying a bottle and they still have to stop and periodically refill the bottle.