It's not really enough to read and upvote, but I'm at a loss as to what I can personally can do about this. So in the spirit of the askhn "how would you turn around Twitter" - let's apply the same thinking to this: "how would you fix the oceans "? There must be some practical steps that one or many of the hn audience can execute?
Try to get other people to do the same.
I find it's hard to do most of these things, and I don't really have much hope that people will change their habits.
Most people don't even realise that they live in an illusion of reality where "everything is possible, you just have try hard enough".