Nearly 1500 people tackled the "beast"— a 7km track over hilly farmland at Haruru Falls that included rolling in swamps and mud pits before being hosed down by firefighters.
The popular Fullers GreatSights Bay of Islands Beast on Friday and Saturday was the Bay's muddiest and toughest race where participants could challenge themselves as individuals of were invited to team up and wear fancy dress.
It was the fourth year the event, organised by Sport Northland, has been held with 450 school students racing on Friday and then about 1000 competing on Saturday. It is the biggest field to date.
Entries sold out a week before the event.
Sport Northland's chief operating officer Brent Marwick said it was the driest year but rain at the start of winter provided the ideal platform for participants to have fun, especially in the swamps and mud pits.