Nobody has released any actual data yet related to that lawsuit. We have anecdotal evidence of illnesses that may or may not be caused by radiation, and may or may not have been due to the time in Fukushima. It seems plausible, but we won't know until they start presenting the evidence.
Speculation in that case is that the desalination plant used to create drinking water sucked in some highly contaminated seawater and they were not monitoring the seawater, while they WERE monitoring the air which was at safe levels.
If this turns out to be true, I would hope the Navy would contract out to retrofit all their desalination equipment with radiation detection capability. I'm kind of surprised it isn't already built-in, and I don't know that it isn't.
You must have missed the video of the sailor setting off the radiation alarms on board the USS Ronald Reagan. He had just been ordered to retrieve the US ship flag as a gift to the Japanese.
The same Japanese who were venting 3 melting reactor cores. All the Japanese could was vent because every single one of their fail safes failed miserably.