Very little, other than the damage to the reputation of Fukushima fish (which is completely unwarranted) and to sales for Fukushima fishermen. This is based in fear rather than science.
Your question mentions contaminated water, as if the water was being pumped straight out of the reactor basements. This will not be the case. It is first treated to remove most radioactive contaminants.
Tepco’s Advanced Liquid Processing System removes highly radioactive substances from the water but the system is unable to filter out tritium, a radioactive isotope of hydrogen that nuclear power plants routinely dilute and dump along with water into the ocean.
Experts say tritium, a radioactive isotope of hydrogen, is only harmful to humans in very large doses, while the International Atomic Energy Agency says it is possible to dilute filtered waste water with seawater before it is released into the ocean.
Also, where did they get this info on “unexamined method”? There are visiting scientists from various international institutes still monitoring Fukushima.
The water has been tested to show that Tritium is the only mildly radioactive ingredient, and THAT will be diluted down by the vastness of the Pacific Ocean. ALPS, the advanced liquid processing system was installed after the triple-core meltdown in March 2011.
Proponents insist dumping will be safe, arguing that tritium emits beta radiation so weak that the health risks posed will be minimal. The industry ministry estimates that even if all the stored water were to be released into the environment over a one-year period, the resulting radiation exposure would be less than a thousandth of that received from natural background radiation. Both methods have track records.
Since both volume and radiation levels can be regulated, ocean discharge of tritiated water is a method routinely practiced at nuclear power plants around the world. In other words, this is something that has been done in water off many nuclear plants previous to Fukushima.