Two weeks ago Mr Peters won the Rotorua round of the Tough Guy gaining entry to the national finals where the top three from each 12km race were invited to compete for the national title.
Even though he came fourth on Saturday he beat his previous best time of 1hr 9min 41sec, by clocking in a time of 1hr 6min 1sec.
He was beaten to the line by Stratford's Nathan Foley, Angus Mckelvie from Palmerston North and Jan Steenkamp from Auckland.
In the woman's event Sarah Mcleod from Palmerston North won in a time of 1hr 16 mins15 secs.
She was followed home by Vicky Paine from Masterton and Annette Watson from Motuoapa.
Peters, 25, said he was hoping to do better and would have another crack at the event next year.
"It was pretty good, a lot harder this time because it was quite wet.
"I was actually hoping to do better to be honest, but it was really good fun, I enjoyed it that's for sure.
"But, I'm pretty sore now, my knees are all scraped up from crawling through those tunnels.
"I'm definitely keen to do it again, it's good to do something different and it's a lot of fun," he said.
It was Peters' first shot at the mid-winter event - he is known more as a mountain biker.
He said it wasn't only the physical challenge, but also the more primeval attraction of wading through mud, that made the event something he wanted to try - and he relied on his existing fitness to get through.
Earlier this year Peters was second in the Lake City Athletics Club senior men's cross-country championship.
He is a former national cross-country mountain bike champion, and was third when the champs were held in Rotorua in 2015. He also won last year's Rotorua MTB Winter series.
12km men:
1st Nathan Foley, Stratford 1:03:55
2nd Angus Mckelvie, Palmerston North 1:04:17
3rd Jan Steenkamp, Auckland 1:04:54
4th Dirk Peters, Rotorua 1:06:01
5th Nigel Payne, Hamilton 1:08:27
12km women:
1st Sarah Mcleod, Palmerston North 1:16:15
2nd Vicky Paine, Masterton 1:17:49
3rd Annette Watson, Motuoapa 1:18:21
4th Roisin McQuillan, Matamata 1:19:03
5th Nicola Carver, Hawera 1:26:22