There are hundreds of nuclear reactors sailing around our oceans in ships and submarines and have been doing so for more than 70 years. Most estimates are above 400 total reactors though the actual count isn't really known since nearly all of these are military vessels.

Operating since 2019/2020:

https://en.wikipedia.org/wiki/Akademik_Lomonosov

It's in the far north, I'm not sure how much fishing is going on around there, or how a potential radiological leak would spread around.