Ukraine is still holding its own despite Russia's hypersonic missile prowess.
If you are talking about a blockade, as we've seen from Russia's invasion, Russia's world's second best navy is already powerless against Ukraine's drone attacks and missiles. And US has already warned China on a potential blockade as being very high cost.
That seems like a massive exaggeration. The Russian navy wasn't that great even before the war. I'm not sure they really have anything going for them besides their submarines, even their single aircraft carrier is permanently under repair and won't reenter service any time soon. Even the Royal Navy is probably significantly strong even on its own.
If you are talking about a blockade, as we've seen from Russia's invasion, Russia's world's second best navy is already powerless against Ukraine's drone attacks and missiles. And US has already warned China on a potential blockade as being very high cost.