How did you arrive at that number? Going by one of the comments in this thread it would be 760 TBq of tritium, which would require 76,000,000 m^3 of water to get below the 10 Bg/m^3 limit of the world health organization.
(granted I don't know where the 760 TBq figure came from either, I'm just trying to get some clarity)
The process for releasing typically dilutes to a standard level before releasing into the ocean/ other water way. So when it's released, it's already at a level you could swim in (drink?), there's no process for it accumulating into a more concentrated form in the ocean, and it has a half-life of 12 years.
