The Ocean around Fukushima is steaming from radiation
coolbuster.net
pic: https://pbs.twimg.com/media/BSyyVi-CIAEsVPy.jpg
coolbuster.net
I'd suppose it's warmer-than-normal water that has been through some sort of multi-stage cooling circuit, just like in any other nuclear plant.
and that leaks are a huge problem - i.e. waste water bypassing the cleaning systems
agreed that there's no proof the mist is steam. But if a normal nuke plant warms up the water enough that fish come to feed there, not hard to believe that in a crisis some steam could rise.
The Fukushima situation is very serious, but spreading baseless rumors out of ignorance is not constructive.