Kyle Allum was camping at the domain on Saturday evening when the large mammal made its way through the campsite.
It was twice the size of a person, and half the size of his car, Mr Allum said.
He was relaxing in his camp chair when the pinniped came down the path from the beach and snuck up on him, which he described as "very scary".
It then proceeded to wander through the packed campground.
"Everyone was in awe," he said.
He said the presence of the mammal was testament to the efforts that have been taken to restore biodiversity in the area, and was optimistic about the ability of humans to share the space with the sea creatures.
On Sunday, a sea lion was also spotted in the vicinity of Doctors Point Rd, in Waitati, where it wandered on to a road and got in the way of traffic.
No one was hurt and it was not known if it was the same sea lion from Warrington.
