Uh, no. Evolution might do this – have humans grow fins – if you can wait a couple dozen million years for that to happen. There’s this thing called evolution that needs to occur.
Basically, no. Humans develop wrinkles, not scales, from sitting in water too long.
We could try a selective breeding program where we get our best swimmers and people with webbed fingers and toes to have children… for a very very very very very very long time.
Don’t “hold your breath” waiting for them to develop scaly tails though.
Or we could unleashing the evil GMO scientists on the project, combining human and fish DNA and seeing what they can clone up.
Depends what you mean “we”, those of us individuals discussing would not be able to evolve to have that capacity. But thousands of generations from now our descendants could have done it.
Isn’t there a Vonnegut novel set in the far future where the sentient beings are similar to seals and other pinnipeds having returned to the sea from humans?