When Alex's eyes adjust to the light and an eagle-like image emerges from the ceiling of the cave, his reaction is one of quiet amazement.
Rachel explains that the drawing shows that Māori were here when the giant pouākai (Haast Eagle) flew the skies in the area. Moreover, the caves provided shelter in close proximity to a rich food source, in the nearby wetlands.
"The wetlands are your supermarket. You're getting your ducks, and you're getting any types of birds, and you're harvesting those birds."
The drawings are both a window on the past, and a trigger for the imagination.
"You can see there's one, two, three… five birds sitting on the wing. Probably carrying their young," exclaims Alex.
Tempting as it is to assign names to the drawings, Rachel prefers to let them speak for themselves.
"It's classed as the bird man, but, is it a bird man?" she asks.
To make her point about allowing for multiple interpretations, Rachel indicates the impressively large drawing spread across the ceiling of the cave.
"There are thoughts around this being the creation story. This figure here being Papatūānuku - the Mother Earth."
Other people, she says, think the three taniwha in the drawing may depict the convergence of the three nearby rivers, and that the image may be a warning to people passing through.
"I don't even like calling it art," says newly-arrived rock art guide Rereahu Hetet (Ngāti Maniapoto, Ngāti Hikario, Ngāi Tahu, Ngāti Mamoe). "This is the science. This is telling you about the world out there and how they would see the world."
The rock art drawings are estimated to be hundreds of years old and are a powerful gift from the ancestors to the generations that have come after them.
"A few generations lost out on learning about these," says Hetet. "With the mahi of Rachel and the team, they've been able to inform the next generation.
After today's visit, Alex is full of awe at the legacy of the drawings and grateful to his daughter for introducing him to them.
"I just can't believe what I've just seen," says Alex, "and knowing that this form of art was done years and years ago. Unbelievable."