Former Dunedin residents David Polson and his daughter Penny, who have lived in the United Kingdom for the past five years, rushed to the aid of the stricken mammal.
Miss Polson, who plans to study marine biology and oceanography this year, said she noticed a "dolphin-shaped piece of seaweed", while walking along All Day Bay, Kakanui, on Thursday morning.
With the dolphin showing signs of life she alerted her father who contacted the SPCA and then the Department of Conservation.
With the incoming tide still 15m away from the dolphin - which was lying on its right side - the pair were advised by Doc to get it to the water as quickly as possible.
Joined by another beachgoer, the trio used a rainjacket to cradle the dolphin, which they estimated weighed 50kg to 60kg, and pulled it towards the water.
"We took it out to a foot and a-half of water and it thrashed around.
"It was a bit disorientated for a while and then it started to kick around and moved around the surf," Mr Polson said.
When it looked like the dolphin was returning to the beach, "we chased it into the surf a bit more", until it swam away, he said.
Doc biodiversity programme manager David Agnew praised the pair for saving the dolphin, which could have been beached for three to six hours.
"It may have made a navigational error, or been chasing fish, and beached itself in the big surf and was left high and dry when the tide went out."
University of Otago marine biologist Dr Will Rayment said thanks to the pair's description the dolphin was identified as being a male juvenile bottle-nosed dolphin.
He said it was unusual for an animal to beach itself and then be refloated successfully.
"Normally they beach because they are ill in the first place.
"These are smart animals and they know where the beach is ... it is very unusual for them to beach and then get away safely."
Anyone who noticed a marine mammal being harassed, or severely injured or entangled, was urged to contact the Department of Conservation hotline on 0800 DOC HOT.
