"We're really excited to this year offer an entirely new course and venue for Mud Muster participants," said O'Connor.
"We've been keeping the new course layout a secret, so the element of surprise will add whole extra levels of fun and excitement to the event.
"As well as new challenges, new scenery, new obstacles and a revamped course, something we can absolutely guarantee, however, is plenty of 'mud' and a 'wetter-than-ever' experience."
For first-timers or those looking for a few fitness pointers, tomorrow morning is the last chance to get a free group training session at Cooks Gardens, being held from 6-7am.
Sport Whanganui and Wanganui Bootcamp teamed up to offer sessions for the past six weeks.
On Saturday, there will be individual racing categories of 3km, 5km or 10km courses. There will also be the new "Mud Mate Teams" section. Spot prizes up for grabs include a Velo Ronny's Bicycle Store bike and a chance to get a hot lap around Shelter View in a V8 Jetsprint boat.
While entries have closed, interested spectators can come along on the day and watch in specific viewing areas.
The action kicks off at 10am and will finish up around 1pm.
To find out more, visit www.mudmuster.co.nz.