Balloon, plastic bags, nylon rope and even rubber thongs are providing a deadly diet for Australia's critically endangered sea turtle population, a new study shows.

On the eve of World Ocean Day, research by the Earthwatch program Turtles in Trouble has shown that 36 per cent of Australian sea turtles are affected by marine litter, with some 18,000 pieces of plastic litter floating on every square kilometer of the world's oceans.

Green turtles are the most common species seen in WA with up to 30,000 females nesting along the coast and along fringing reefs at Shark Bay to Murchison River between October and February each year.

According to the WA Department of Environment, divers may see large juveniles around Rottnest Island reefs.

University of Queensland marine biologist Dr Kathy Townsend said the problem of marine waste had to be tackled before the already low population numbers of sea turtles became even more depleted.

"This thing is everyone's fault, and because it's everyone's fault no one takes responsibility," Dr Townsend said.

"We need to stop generating so much waste. We are doing the inconceivable, we are starting to fill up the oceans of the world."

The Turtles in Trouble program found turtles had swallowed balloons, plastic bags, nylon rope, styrofoam and thongs, among other things, possibly mistaking them for jellyfish.

Once ingested, the plastic causes a gut impaction which leads to the contents of the animal's gut decomposing.

"The animal becomes positively buoyant and it can't dive down to eat, it can't get out of the way of predators, it can't get out of the way of boats, so it really is quite a tragic thing," Dr Townsend said.

It can result in so-called "floating syndrome", where the turtle may take months to gradually starve to death.

"It's a really long, drawn-out, painful death," Dr Townsend said.

Earthwatch Australia executive director Richard Gilmore said a number of measures can be taken to reduce marine rubbish.

"Australia's marine environment is absolutely fundamental to our economy, our environment and to our way of life," Mr Gilmore said.

Dr Townsend said that everyone can do their share. "Start refusing those items that have a useful lifetime of only minutes and yet take years if not decades to degrade," she said.

"Do you really need to have a plastic top on your paper coffee cup? Refuse that, you don't need that".

Marine rubbish also affects Victoria's famous fairy penguins, which frequently get entangled in debris.

Dr Townsend said if the problem is not addressed it will only get worse, but with awareness, she hopes the correct choices will be made to reduce the amount of rubbish reaching the marine environment.