"It seemed like a baby one. It didn't seem that big, but obviously big enough to scare anyone out the water. It just seemed to be swimming back and forth."
Mr Aguilera said the shark kept swimming in the area for at least 15 to 20 minutes.
He said it was the first time he'd seen a shark at Papamoa.
Onlookers were thrilled, and not a little scared, to see the shark so close to the popular beach, Mr Aguilera said.
"Obviously it's exciting, but it's pretty shocking. In fact, Kate wanted to go in for a swim and I was just like, 'No, I'm definitely not going in.' And actually after that, once it went away, we stayed for like half an hour, 45 minutes, and there was no-one going back into the water."
Mr Aguilera said he'd rather not see the shark again.
"I hope not... we still want to go for a swim without having to check constantly if there's a fin around."
Although the fin piercing the sea's surface and reports of swimmers running for safety may spark memories of the movie Jaws, shark attacks in New Zealand are rare.
According to Te Ara, the Encyclopedia of New Zealand, there has never been a shark attack at Papamoa, or anywhere in the western Bay of Plenty.
The Shark Attack Data website says there have been only 24 fatal attacks in New Zealand since 1850.
Department of Conservation marine scientist Clinton Duffy said yesterday's shark was a bronze whaler (Carcharhinus brachyurus).
He said "bronzies", as they are commonly known, were relatively abundant in the Bay of Plenty and there were sightings like the one at Papamoa every summer.
"Although they can become aggressive towards spear fishers when stealing fish off spears and floats, they generally ignore swimmers and other water users. Most divers that I know consider them harmless, but their size and power mean they can be dangerous if provoked."
Mr Duffy, who is studying great white sharks as part of his PhD studies at Auckland University, said bronzies reached a maximum length of 3.3m and might weigh more than 200kg.
"They feed primarily on fishes, including mullet, kahawai, snapper and eagle rays. It is very common to see them in the surf zone like this and they can be encountered well up estuaries hunting over tidal flats at high tide."
Although local fishermen have previously told the Herald that bronze whalers are the most common sharks hanging around Papamoa, last week a blue shark was caught there.
Tauranga Land Based Fishing organiser Jackson Brown said that fish was spotted just off the beach.
Mr Brown had earlier told the Herald he'd seen six bronze whalers in one day.
Last week, fisherman Russ Hawkins, who owns Fat Boy Charters, said he'd seen mako and blue sharks in the area this summer.
