BBC: It's more than five years since the earthquake and tsunami off the coast of Japan caused a huge leak of radioactive material into the world's oceans.
Workers battled to prevent the Fukushima nuclear plant going into complete meltdown and radiation levels rose by a factor of tens of millions.
However, a new report by Australian scientists has revealed that radiation in the Pacific Ocean is rapidly returning to normal and should be at its previous level by 2020. So what does this say about radiation...