Protesters - who were asked to bring their own homemade banners - carried signs reading: "we love our beaches", "deep sea drilling is not worth the risk", and "Anadarko go home".
One of the more inventive ones likened Anadarko to anaconda snake oil.
Steve Abel, Greenpeace climate campaigner, said the protest, which begin at midday, was "amazing".
"There's been an incredible turnout," he said. "The creativity of some of the banners - humorous, pointed, and totally inspiring."
He said people felt "very strongly" against deep sea drilling.
"We have this incredible potential for clean energy [in New Zealand], we are actually a power house on clean energy, so it's just a no-brainer for people," he said.
Kiwi legends at South piha #OilFreeSeas #bannersatthebeach pic.twitter.com/sAF4XRkKel
Many felt the full economic potential and the possibility for New Zealand to become a world leader in green energy would be lost if the government focussed on deep sea oil drilling, he said.
"The Government will be getting a very strong message today that this drilling is not wanted, and Anadarko will be getting that message to."
If Prime Minister John Key's cabinet didn't see that, they have "really got their heads in the sand", he said.
New Zealand women's national surfing champion Micha Davis and Labour MP Phil Twyford also spoke at the lead event in Piha.
Protesters joined hands to form a human chain from the land to the sea, and a haka was also performed.
