He said the biggest barrier was that a lot of families could not afford to pay for the bus to get them to the event.
"It's a major issue. It's an access issue."
The $10,000 grant from Auckland Airport would pay for children at the surrounding low decile schools to get a bus to the February event.
"We invite low-decile schools first and there's an obvious reason for this. If kids have never been to the beach then you can't engage them to change their behaviour about what they're doing outside their house in terms of littering because it goes into the stream. That issue is prevalent in areas surrounding the Manukau Harbour and we are very aware of this from experience."
Manukau Harbour extends along 450km of coastline and the Sustainable Coastlines clean-up runs for six weeks, with an estimated 1500 students helping out.
As part of being involved in the clean-up, the students are given an educational presentation before boarding the bus. They then help pick up the rubbish along the shore.
Auckland Airport said staff are also involved in the airport's own clean-up of the area of the Manukau Harbour surrounding the airport so it was keen to partner with the charity to expand its work.
Auckland Airport general manager of people and safety Anna Cassels-Brown said: "We're proud of our airport's location on the beautiful Manukau Harbour and we are looking forward to partnering with Sam, his team and local schools to continue to protect it."