The Lake Macquarie resident has swum, snorkelled and scuba dived around Nelson Bay for more than 20 years and has become alarmed at the increasing quantity of plastic and rubbish she has seen and collected from the water over the last few months.

"It is undoubtedly on the increase," she said.

"I come back from each swim with a wetsuit stuffed full of rubbish.

"Whilst it's uncomfortable for me, it is deadly for green sea turtles."

Ms Rossiter keeps an eye on two 10-year-old green sea turtles, an endangered species, which frequent the water at Fly Point.

Kelpie and Stripy are monitored by the Department of Primary Industries.

The green sea turtle has a downward facing spine in their throat, so while they can swallow things easily, they can not bring them up.

Ms Rossiter said she is worried the turtles would mistake plastic floating in the water for a jellyfish and eat it.

This would paralyse the turtle's digestive system, preventing them from ingesting good foods.

Ms Rossiter hopes to gain the support of businesses in putting up signs saying: "do the right thing, put your plastic in the bin" in shopfronts.

She said she would approach the council to install better signage around popular waterfront spots prompting people get rid of their rubbish correctly.

"We need to join forces as a community, with the public, businesses and council . . . to raise awareness about the damage our littering is doing to the marine environment and its inhabitants," she said.