Across the Pacific Ocean, radiation levels are swinging back to normal following the meltdown at the Fukushima nuclear plant, which contaminated the sea with gases and liquids, a study showed.

Dozens of reactors were shut down after an earthquake, of a magnitude of 9.0 triggered a tsunami on March 11, 2011. It seemed to ring the death knell for the ocean, which got overwhelmed with nuclear material.

After the explosion, seawater that was used to cool the reactors just transported radioactive elements back to the Pacific Ocean. Currents dispersed the material widely.

A review by the Scientific Committee on Oceanic Research, which got a number of experts from all over the world, conveyed that radioactive material had flowed even up to the US.

Still, examining 20 studies of radioactivity associated with the plant showed that radiation levels in the Pacific were coming back to normal following a rise tens of millions of times more.

"As an example, in 2011 about half of fish samples in coastal waters off Fukushima contained unsafe levels of radioactive material," said Pere Masque, who co-authored the review published by the Annual Review of Marine Science.

"However, by 2015 that number had dropped to less than one percent above the limit."

The seafloor and harbour near the Fukushima plant seemed to be still contaminated.

"Monitoring of radioactivity levels and sea life in that area must continue," added Masque, a professor of environmental radiochemistry at the Edith Cowan University in Western Australia.

The disaster hit Japan hard. Even now, there are heavy efforts to rehabilitate the displaced people, along with making the area habitable again.