In this Perspective, Ken Buesseler describes the enormous challenges that remain in doing clean-up on land in Japan following the Fukushima Daiichi Nuclear Power Plant disaster in 2011, even as some progress has been made offshore. Buesseler notes that among the biggest unresolved issues is what to do with the more than 1,000 tanks at the plant site that contain contaminated water. One possible option for dealing with it is to release it into the ocean. It contains Tritium, 3H, which is notoriously difficult to remove because it is a radioactive form of hydrogen that is part of the water molecule itself. But, says Buesseler, while tritium has received much attention to date, the tank water also contains other radioactive isotopes that behave differently in the ocean and are more readily incorporated into marine biota or seafloor sediments. Buesseler argues that, to assess the consequences of releasing the tanks, "a full accounting ... of what isotopes are left in each tank is needed." Buesseler also suggests that options other than ocean discharge should be considered, moving forward. And he notes that public fears about the clean-up process "should not be dismissed" because these decisions may have negative impacts on local fisheries that are just now rebuilding.