The penguin was released from the research vessel Tangaroa on Sunday morning about 50 miles (80 kilometers) north of remote Campbell Island in water about 935 feet (285 meters) deep.
Wellington Zoo veterinarian Lisa Argilla said Happy Feet needed some "gentle encouragement" to leave the purpose-built crate that had been his home on the boat for six days. He slid down a makeshift ramp backward and then took off.
The bird was discovered June 20 on a New Zealand beach far from his Antarctic feeding grounds. He became sick from eating sand and was transferred to the Wellington Zoo. His story has captured the imagination of people around the world.