Happy Feet is to head home at the end of the month, ending a two-month stay at Wellington Zoo.
Zoo spokeswoman Kate Baker said the emperor penguin was doing well and had even managed a few quick dips.
"He's very perky. We opened the slide up to the saltwater pool [on Sunday] because it's snowing in Wellington. He had a swim [on Sunday] night briefly."
She said staff coaxed Happy Feet into a second swim yesterday morning, which showed he was making excellent progress.
"Because he's swimming it shows that he's got good waterproofing."
Happy Feet now weighs 26.6kg, having put on 4kg since his arrival.
He has spent the past seven weeks in the care of Wellington Zoo since washing up on Peka Peka beach, north of Wellington, in June.
He has had many procedures performed to flush sand, rocks and liquid out of his stomach.
The zoo will today announce how Happy Feet will make the more than 3000km journey back to the Antarctic.
"It will be really rewarding to see him being released back into the wild," Ms Baker said.
An "army" of zoo staff ranging from the vet team to property staff had been working with Happy Feet, she said.
He is expected to leave at the end of the month.
Travel options previously floated have included a combination of refrigerated truck, boat and air travel, ending with his release at a point beyond Stewart Island.
The famous penguin is the second known to have landed here. The other landing was in 1967 when an emperor penguin was found on Southland's Oreti Beach.