Metal nails, a discarded trolley and an old boat battery have their place in the scrapyard. Instead, these items ended up in a watery dumping ground: The Sisters' Islands Marine Park.
In just 45 minutes on Sunday, 20 divers collected more than 72kg of trash there, including plastic bags, disposable cutlery and wire mesh.
"It is surprising to find trash like the trolley and battery in the marine park, and it could be even worse in places that are not frequented by divers," said marine biologist Toh Tai Chong, who helped organise the event.
The volunteers did the underwater clean-up at Singapore's only marine park to mark World Oceans Day today.
The information from the clean-up was uploaded onto Dive Against Debris, an online portal which collates international marine trash data run by Project Aware - the environmental arm of the Professional Association of Diving Instructors.
Dr Toh, who is from the National University of Singapore's Tropical Marine Science Institute (TMSI), told The Straits Times that such data helps to give a better picture of the regional trash situation.
For example, identifying trash "hot spots" could help conservation groups zoom in on the areas which need the most urgent action, he said.
An estimated eight million tonnes of plastics enter the oceans every year, said Ms Kakuko Nagatani- Yoshida, the Asia-Pacific coordinator for chemicals and waste at the United Nations Environment Programme, and Asian countries are among the worst culprits.
Everyone can make a difference she noted, adding: "Multiple solutions are possible, including avoiding single-use and non-essential plastic items in our daily lives and investing in better solid waste management on land."
Even though underwater clean-ups have been organised before, this was the first community-led one involving multiple partners.
Organisers included TMSI, dive centre The Submersibles as well as conservation group SeaKeepers Asia. The National Parks Board (NParks), which manages the marine park, as well as the Maritime and Port Authority of Singapore (MPA) supported the event.
Other than collecting trash, the volunteers also helped to rescue corals by picking up fragments that had been dislodged from the reef, and transferring them to NParks' coral nursery, which is also at the marine park south of the mainland.
"Eventually when they grow bigger, the corals will be attached onto artificial reefs there," said Dr Toh, whose research shows that coral fragments placed in nurseries could be transplanted to reefs to improve the habitat.
Said Dr Karenne Tun, director of the coastal and marine division at NParks' National Biodiversity Centre: "The two activities involve community volunteers and are very much aligned with our objectives of conservation, outreach and education at Sisters' Islands Marine Park."
Added MPA chief executive Andrew Tan: "For us, keeping the environment clean is as important as making sure that we are also the world's No. 1 port."
• To find out more about the marine trash situation, visit http://www.projectaware.org/diveagainstdebrismap