Steven Hooper was metal detecting when he heard muffled voices coming from below.
Deciding to investigate further, he was shocked at what he stumbled upon. A couple and a dog living in a cave, which was decked out with solar lights, a fireplace, bed, lounge room, and garden.
Mr Hooper, who films his adventures for his YouTube channel, documented the experience.
"As I finished metal detecting I wanted to check to see if there was any caves because it looked like the ground where I normally find caves," Mr Hooper, from Mandurah in Western Australia, explained.
"As soon as I stepped down and walked around the cliff edge, I saw a cave. I walked up to it and that's when this couple and their dog greeted me.
"They gave me a tour and showed me a tunnel near their cave."
In the video, the pair can be shown taking Steven to a secret tunnel, which used to be home to a soap factory.
"It's an old soap factory tunnel that went through the limestone to the back of the factory," Mr Hooper said.
"They would wheel or cart stuff through the tunnel as there is wood planks down. It goes all under the streets of Fremantle."
Mr Hooper said the positive interaction had motivated him to help out the homeless.
"They didn't have much yet they were beyond happy compared to others. It softened my heart," he said.
"The experience has changed me. I started re-evaluating all the random stuff I own because those guys were happy with very little.
"It gave me a reason to try and see if I can start helping the homeless.
"I want to give people struggling something to help and start a GoFundMe. I'm thinking of possibly doing live videos on my YouTube to raise money for a foundation that helps out the local homeless people."
Mr Hooper said anyone who thought badly about the homeless should "spend five minutes" talking to them.
"Get to know them and find out why they are now in this difficult situation because they're not bad people," he said.
"The couple I met were the happiest and most humble people I have met in a long time."