It just seems like it would be a really cool thing to have gills and be able to populate the oceans in the same way we populate the land. We could have houses and shops and vehicles, andgo on walks/swims and just kind of live underwater.
Start a whole new second species of human here on earth maybe, Who knows?
Yes, but being able to change genetic code does not mean being able to design entire organs and pop 'em in there during fetal development. That would be very challenging.
Gene editing has the most positive potential when it comes to things like curing/eradicating genetic diseases, doing microbiological research, or engineering metabolic products in microorgsnisms.