AFAIK a sunken reactor is not as big of a threat to life as a one (marine or land-based) that releases nuclear material in the atmosphere, so the biggest issue should be what may happen before the reactor sinks.
Anyway IMHO the biggest issue with nuclear is not its safety, but rather that, even when it operates without the slightest of incidents, it produces waste that needs to be kept “safe” for periods of time that exceed the age of most nation states (let alone private companies).
It’s true waste can be a problem. Incidentally, that’s one reason why thorium is a far better fuel since the waste is only dangerous for around 500 years compared to thousands of years for uranium.
only dangerous for around 500 years
That “only” is just ridiculous :)
Just try to imagine the history of a nuclear waste storage site from the 1500s… how many budget cuts would have it seen? how much buck-passing when it changed hands as a result of war of revolution? how many times would it have been bombed? (and it’s not like we’ve had bombing for a very long time).
We are just not responsible enough to play around with nuclear. Hell, we are showing we are even not responsible enough for hydrocarbons.
(yes, I do know some amount of nuclear waste, from medical applications etc., is definitely worth it and unavoidable - let’s just keep it to a minimum)