It was once thought oceans were so vast they could not be affected by humans, but unfortunately rapid globalisation now threatens marine biodiversity. The negative effects of marine debris were recognised in the 1970s, and more recently globally acknowledged in scientific literature. We revisited the Greater Sydney region in New South Wales Australia, to research whether plastic waste on coastal beaches has reduced in recent years. This was achieved by designing a community science project in collaboration with local schools and volunteers. We discovered that plastic debris differed between beaches and strata, but was similar to Australian beaches that were sampled over a decade ago. The high correlations we found between plastic debris and both the frequency of storm-water drains and local population sizes suggested that storm-water drains may be responsible for delivering plastic waste to coastal ecosystems, and the amount of plastic debris was proportional to the size of the surrounding population. Involving local communities has the potential to rapidly raise awareness about key conservation issues to large and broad demographic audiences. Ultimately, this may inspire public and political change.