The New Zealand Sea Lion Trust organised the beach clean-up in partnership with Tomahawk Smaills Beachcare Trust and Aotea Electric.
New Zealand Sea Lion Trust social media liaison Hannah Zwalue said the amount of rubbish collected from the beach was "just ridiculous".
"We cleaned this area up just last year.
"So, this is only 12 months worth of rubbish, which is crazy.
"It’s shocking and just really disappointing, to be honest.
"I think the bottles has really shocked me though. People just sit and have a drink and throw them — that’s just not cool."
She said the trust was completely reliant on volunteers and donations.
"We don’t have a lot of funding and we run off donations from the public and we’re just trying to increase advocacy and education around these awesome marine mammals.
"We’re pretty lucky to have [sea lions].
"There’s not many other cities in New Zealand, let alone the world, that have a marine mammal that call the place home and I think the interaction between humans and sea lions is going to increase.
"As coastal users, we need to be aware of them and start thinking of ways to protect them."
She suggested a good way to help protect the sea lion habitat was to increase signage around the area and have more prominent placement of bins.
"Over summer time, we had nine pups in the area and on the road, in the habitat there, and we had lots of adults, both male and female."
Just last year on Boxing Day, a sea lion named Huna was discovered dead on the side of the road near Smaills Beach.
"Huna was a male sea lion who was just 4 years old and he was hit by a car and died."
Ms Zwalue urged the public to make sure to pick up after themselves to better protect our native taonga species.
"[The sea lions] are on their bellies a lot of the time, they’re getting cut up by glass.
"They’re having pups pretty much in the plastic, and this is going to be the future."
