I have done both scuba and snorkeling in my main 3 acre pond and this one acre RES/SMB pond snorkeled once last year.
Problem is the water is almost never clear enough to see anything very well. Because of the excess bushy pondweed in this pond it was actually clear enough to see maybe 3'. Problem is at 3' visibility you can really only see "well" about 18". Things beyond that are more just fuzzy shadows. We did see SMB last year snorkeling but the only way we ended up seeing them is by placing floating feed on the surface and being in the middle of the feeding frenzy. Then we could see flashes of fast moving fish. Not really a clear view. I did find some fingerling RES maybe a couple inches long in among the bushy pondweed.
One year in the main pond in late summer the water cleared up to about 3' and I crawled around in 2-3' deep water and saw lots of BG on beds. I could actually creep up towards the beds slowly and the fish would get used to me and stay on the beds. That was kind of cool. I would get a big male BG to "charge'" me to try and run me off. Took a bunch of video with a go-pro but I had the camera upside down so all the video was upside down, LOL. I did find one nest out by itself in another location that was a RES nest. I could see the red opercular tab. Problem is to see them really clearly in 3' visability you need to be within about 18" and the fish will not let you get that close. About as close as they would let me approach without leaving the nest was probably 2.5', so I could see them but not terribly clearly. Was still fun.
Under water in fresh water at least, fish can see and sense you are there long before you can see them. When I used to competition spearfish in Tablerock lake, the rough fish we targeted always knew you were there but I could not see them. If you scuba dive and swim all the time it is likely you will never see a fish. The way we spearfished is to drop to the bottom, lay as still as we could on the bottom or in a submerged tree, try not to even move your eyes. The fish would get curious and start circling in. You would see first a shadow on the outskirts of vision pas in front of you. Then just hold still, They would circle around and the next pass come closer. Once you were able to get a positive ID (so we did not shoot a game fish which is illegal) we could shoot if they were in range of the gun. Funny thing is, clear water was a lot harder to shoot fish than muddy water. We had retaining strings on the spear about 6-7' long. Spears lost a lot of velocity at the end of range and if the tip hit a big carp scale some times would not penetrate the fish. In muddy water we would hold the tip of the gun right under our our face mask. Pneumatic guns, not the rubber band guns like used in the clear ocean. If you held the gun out in front of you, the fish might pass between you and the spear tip. So if it was extremely muddy we might have the spear tip just inches in front of our face mask and shoot a fish that was maybe 2' in front of our mask. Best fishing was when we were shooting fish about 3' in front of us.
I was never very good at it. My partner brother was a lot better. We did scuba spearfishing one day and skin diving spear fishing the other day. He could hold his breath a lot longer than me. Dropping down in 3-10 feet of water, holding your breath till you get a fish or as long as you can, then doing it again and again is not easy. But there were some guys that were really good at it. I think is was 4 hour competition and some of the really good spearfishers could bring in 50 or more fish. I was usually lucky to get a few. We could shoot any rough fish which included carp, suckers. drum. buffalo and shad.
But I digress. The trick to seeing fish in lakes and ponds is not swimming to look for them. It is holding still and letting the fish come check you out. Fish are curious. Bluegill you will feel biting on the hair of the arms and ears before you see them. Then eventually if you hold still small ones will come peck on the mask faceplate. It is really hard to see the larger fish unless they are on the nest. They are much more wary than the little ones. I have successfully fed them by hand though. Had foot long CC come right up to take feed. If you do it often enough (I did not) you can get CC tamed enough to eat out of your hand. In Beaver Lake in a cove the divers there had several pet CC that they took hot dogs down and fed them. They would come right up to a diver looking to be fed. So if you work with the fish they can be tamed to the point you can see them. For the average person just jumping in with a mask, it is a good chance they will never see a fish unless they hold still.
