I also use the above method for removing things from an image. Say you UW pic of a fish, you have a photobomb of another diver giving you an OK signal.
But you really want a pic of the fish & the corals, minus the diver...
Using the various tools in PS on the original might seem the way to go, but you'll be creating lots of artifacts. Instead, make a copy, work on a TINY version, remove the diver, then blow up the copy back to the original size, and use the new image as a layer on top of the original image.
Then delete from the "on top" layer which is the tiny-diver removed-blown-up everything except where the diver is.
Basically your "removed" diver image has a "better" ocean, pixel-wise, than using a "copy" tool to "paste" bits of ocean here & there on top of the diver.
Plus, this technique is WAY faster, and there are many variations.
Let's say the original image is 4000x3000 pixels, and the diver is 3x as big as the fish, I'll reduce the copied image to where the fish would be in the 10-15 pixel range in size.
Meaning, only about 50-60 pixels of diver to remove, instead of some 1500-2000 pixels.
You're creating artifacts with the stamp tool, in the tiny version, blur the "stamped" area 1x or 2x, then blow up the 400x300 image back to 4000x3000. No more artifacts.
I can remove a diver in about a minute, for simple cases.
Why I like Lightroom for post-processing - I can layer "changes" of various brush sizes, on top of each other, instead of layering images and doing addition or subtractions. I can't remove a diver using LR, but I can easily darken him to oblivion and make the fish stand out.
Sometimes that's good enough.
In LR, have not had good success (like none) with sharpening effects.
Best-bet - always shoot multiple images while on location of the "same" subject. So you can layer up multiple, different, images and keep / lose from the bunch until you have an overall good pic.
So in my example, we have "Bob the Diver" photobombing your awesome pic of a king-sized Queen Angel fish (pun intended).
Simply stay put, wait for "Bob the Diver" to float away, then take another pic of the same spot, at the same angle, as close as possible.
Just so you have "ocean" or "coral" background to add to your original image to paste on top of "Bob the Diver", by layering the two images together.
Or, make a pic of "Bob the Diver" with a giant sea-turtle w/o the giant sea-turtle, and tell him you never saw a turtle...