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?
This is the whole “if humans were going to have wings we’d have to redesign the whole organism from the ground up” fiasco all over again.