It seems so but it is a large pool of highly radioactive water. I wasn't sure so I did the math:
Seawater contains about 12Bq/L of radioactivity naturally and this spill contains 230MBq/L, that's a factor of nearly 20 million. Bringing this back to the total volume of the oceans (around 1.3x10^21L), this spill has a radioactivity equivalent to around 1/650 millionth of the ocean's contents.
At first glance one in 650 million might not seem like a lot, but several other spills have already happened, and a very large amount of water is not even contained at all and directly spilled in the ocean or underground. It won't remain unnoticed if we keep this up for too long.