tl;dr : the earth has been gradually flooded, over the course of a few hundred years. Also, there are now large lumps or ice raining out of the sky (not very often), causing massive tsunamis.
I have recently watched a sort-of documentary, about what would happen if a roughly moon-sized icy asteroid collided with the moon, causing icy shrapnel of various sizes to rain down, smallest first. The long-term results are that the entire planet gets flooded, even mount Everest, due to the smaller chunks of space-ice depositing huge amounts of water-vapour in the atmosphere, resulting in "biblical flooding". After the rain stops, the larger chunks start falling down, causing massive tsunamis. Humanity has moved to floating cities, which can survive these waves, by riding over them. Probably not comfortable, but survivable.
My question is what weather would look like during and after this period of mega-tsunamis. My question is not about what we would do, but what our problems might be.
A theory I had was that there would be constant (as in Stormlight archive Highstorms. Not Star Wars Kamino) hurricanes, since there would be no land to stop them. Also, currents should be interesting.
Note: I have tagged this question with planetary-rings, since that is where all the water and tsunami-causing space-rocks come from.