A volunteer underwater clean-up project at Manly Cove is recovering hundreds of drinking straws from the sea and raising awareness of single-use plastic pollution.

Dive instructor Harriet Spark is the project's organiser and is involved in the local environmental group Sustainable Organisations of Manly (SO Manly).

She was inspired to start the clean up after one of her colleagues recovered more than 600 straws during two short snorkels at Manly Cove.

"On one of our dives we actually found an octopus holding four straws in its tentacles," she told Josh Szeps on ABC Radio Sydney.

Clutching at plastic straws

Operation Straw invites volunteers to snorkel and recover discarded straws at Manly Cove. ( Supplied: Harriet Spark )

Ms Spark was alarmed at the amount of straws found in the cove and started "Operation Straw" to combat the pollution.

"When it comes to items like plastic straws, these items that we used for just seconds and at most minutes, they last on the planet for hundreds and hundreds of years.

"They're a bit of an unnecessary item that we can stop using."

She invited volunteers to collect the straws and record their colour which provides clues as to where the rubbish is coming from.

"One of the big offenders is the McDonald's straws; we find a lot of them," Ms Spark said.

"The data is the most important part of it because if we continue to clean the beaches and don't record what we find, it's hard to drive change.

"But if we record what we find, we can make a big difference."

Changing user habits

Volunteers collect data on the colour and length of the straws to trace where they originated from. ( Supplied: Harriet Spark )

The volunteers have already collected more than 1,200 straws from the cove after seven clean-up events.

"To put it into perspective, these straws end to end would stretch roughly the length of three Olympic swimming pools," Ms Spark said.

The majority of the discarded straws originated from nearby, but could also be washing in from the greater Sydney Harbour area, she said.

The data collected from the project will be used to encourage local businesses to change the way they dispense straws or eliminate their use altogether.

"Even just putting straws behind the counter and having some signage explaining 'we only give out straws when asked' — that reduces straws hugely," she said.

"Just making a few changes can make a big impact."

Volunteers have recovered hundreds of plastic drinking straws during the clean-up at Manly Cove. ( Supplied: Harriet Spark )

No reduction in plastic waste over 25 years

Richard Nicholls has been running a dive store in Manly for 25 years and his business partnered with the volunteers to reduce the plastic waste in the cove.

Throughout his career he has been heavily involved in underwater clean-up initiatives but witnessed little reduction in the amount of plastic being recovered.

"We pretty much get 1,000 kilograms a year from pretty much one spot in Manly Cove," he said.

"It's sad in a way. We always hoped that the amount would drop and for a while we thought it was dropping, but all that was happening was that we were getting more efficient at picking up rubbish from that spot.

"So we just widened our search area a little bit and basically produced the same results."

Richard Nicholls has been actively involved in clean-up projects throughout his 25 years in the Manly area. ( Supplied: SO Manly )

Mr Nicholls expressed concern about how the discarded plastic was affecting marine life and the flow-on effect to humans.

Tips for reducing plastic straw use Ask hospitality staff to serve your drink without a straw.

Ask hospitality staff to serve your drink without a straw. Bring your own reusable metal, bamboo or glass straw for use at cafes and bars.

Bring your own reusable metal, bamboo or glass straw for use at cafes and bars. Request venues to go straw-free or use environmentally friendly alternatives to plastic. Source: Plastic Free Manly

"When I was a kid in the '60s, the sea was the biggest rubbish dump in the world; people just threw everything in the sea without any thought of what could happen," he said.

"Now we're seeing the results of plastic pollution and the major problems that we're going to have as more of that gets in the food chain and people start ingesting plastic."

After years of witnessing the pollution up close, he urged all plastic users including manufacturers, businesses and consumers to do their part for the environment.