"The ferries are busy and Fullers is doing a great job moving vessels around to cope.
"We always made it clear the ferries would be busy and operate on a first-come-first-served basis."
Fullers360, which operate ferries around the city had, as of 4.30pm, transported more than 21,000 people across all its services.
A spokesperson said 12,000 had travelled on the Devonport route alone, compared with a normal winter Sunday when the route sees 2500 passengers per day on average.
"We've seen thousands of people travelling the harbour and exploring Auckland with us today – with Devonport, Half Moon Bay and Hobsonville Point being especially popular destinations," the spokesperson said.
"Fullers360 is proud to be supporting Auckland Transport's celebration of public transport and providing free rides on many of our ferry routes today.
"It's been a great day, with our staff and crew working incredibly hard to get customers where they want to go. Thanks to everyone for travelling with us and making it such a memorable day."
A Devonport cafe worker, who did not want to be named, said it was "crazy and chaotic" this morning - but things were getting under control around 2pm.
"There's still a queue, but it's just like the normal queue you get on a typical work day," she said.
"It's still very busy compared to a (normal) Sunday though."
As well as all buses and trains, most ferries are free, including Auckland to Devonport and Auckland to Hobsonville. However, Waiheke ferries are only free for people who already hold multi-passes to the island.
Passengers must still pay for ferries to Rangitoto, Tiritiri Matangi and Motutapu, as well as the Skybus to the airport.
