In the case of nuking an offshore oilrig, the parts per million of irradiated water would be negligible after they're dispersed through the oceanic currents. It would get spread out too much to do any major damage after the initial blast. Anyways, they're Russian. They probably dump some vodka in the area, and if the S.T.A.L.K.E.R games have taught me anything, that will solved the problem right away.
but if they used it too much, the radiation could get pretty high right? Anyways, its an awewsome idea. Make sure to spill some oil on top of greenland next
Yeah, there is a finite amount, but you gotta remember, there's trillions upon trillions of litres of water in the oceans. Also, this: