In order to live under water; I think we'd need to develop some sort of gills, or spend tons of money on the development of under water living facilities. That doesn't seem worth while. It'd be easier to continue living above water. Assuming that this question implies that the ice caps melt, and the water levels rise: I'm sure there will still be land that's not covered by water, and that'd be where people live.
I don't really see why we would want to live underwater. The most evolutionary advanced species are on land and going back underwater seems like a step in the wrong direction. If it comes to it, with an extreme change in our planet that we can't see yet, yes I think we could survive living underwater with enough time to prepare and engineer facilities.
Assuming that this question implies that the ice caps melt, and the water levels rise: I'm sure there will still be land that's not covered by water, and that'd be where people live.
If it comes to it, with an extreme change in our planet that we can't see yet, yes I think we could survive living underwater with enough time to prepare and engineer facilities.
lol