WELLINGTON - The emperor penguin dubbed Happy Feet was released back into the Southern Ocean on Sunday.

The bird was released at 10:30 am New Zealand local time on Sunday, 49 miles due north of Campbell Island.

In this handout image provided by NIWA (National Institute of Water and Atmospheric Research), "Happy Feet", the emperor penguin who became lost and ended up on a New Zealand beach prepares to make his return to the sea, on September 4, 2011, at sea off Campbell Island, in the Southern Ocean. The penguin has been fitted with a tracking device so that researchers can continue to monitor his progress. [Photo/CFP]

The penguin was released down a purpose-made 'hydro-slide' off the stern ramp of the research vessel Tangaroa, when other options, including using an inflatable boat, could not be used because of the rough seas.

The National Institute of Water and Atmospheric Research said the release went without a hitch.

Wellington Zoo manager of veterinary science, Lisa Argilla, said Happy Feet needed some gentle encouragement to leave the safety of the crate that has been his home for six days.

"He slid down his specially designed penguin slide backwards but once he hit the water he spared no time in diving off away from the boat and all those 'aliens' who have been looking after him for so long," she said.

The penguin came ashore exhausted and hungry at Peka Peka beach north of Wellington in June and was nursed back to health at Wellington Zoo.

He travelled in a travel crate specially designed to keep him cold and comfortable during the voyage, and has been treated to hoki for his meals and fresh ice put in his crate each day.