Both Penn and Macintosh live nearby and take lessons there.
"I've been riding on and off since I was about seven years old," Macintosh said.
"There have been a couple of riding schools along the way, but now I can take lessons down the road from where I live."
Currently, they share an off-the-track thoroughbred called Simba.
Penn lives next door to Macintosh and began riding at a similar age.
"I grew up around horses, but I took a little break when I moved from Wellington to Whanganui.
"I got back into it with Bea just under two years ago."
The team already has a six-hour trek under their belts, as well as several beach rides.
Whanganui Cancer Society fundraising and event co-ordinator Sophie Westacott said both Penn and Macintosh had lost grandmothers to cancer.
"They are doing something they love to raise awareness about this hideous disease that affects the majority of people in one way or another."
They both would likely do at least 12 hours individually every week, Westacott said.
"It's not just about them riding the horses either, it's the taking care of them and re-adapting them.
"This is what these girls do in their free time."
In the spirit of Relay Your Way, teams were welcome to go as far over the 12-hour time frame as they wanted, Westacott said.
"Bea and Sophie are going above and beyond their goals already, which is amazing to see.
"If Covid-19 has taught us anything, it's that you can pivot your way."
As of Tuesday, there were 14 teams made up of 59 individuals taking part in Whanganui Relay Your Way.
This year's event runs until April 2.
Teams can sign up at www.relayforlife.org.nz/whanganui