A hydration pack or belt with a minimum capacity of 1L (1000ml) is mandatory/compulsory for all racers doing the 50k Ultra. It is highly recommended for the 21k Beast due to Australian extreme hot weather conditions.
Water stations are available on the course but it can be several kilometres between water stations. For your own safety, you can't rely on these as your only source of water. A Camelbak-style hydration pack is best as it leaves your hands free, and hydration belts are also a good alternative.
For the shorter race distances (5k Sprint and 10k Super), a hydration pack is still strongly recommended, especially in warm weather.