I think a red filter would be better for SCUBA, but is not necessary for snorkeling. I bought one for shallow depths and it was still too much for water no deeper than 20 feet.
As for the quality of the pics, realize that I cleaned them up in Lightroom. The visibility when I shot the sea turtle was terrible. I'm shocked that I was able to clear up as much as I did. The sting ray was shot in clear water at about 3 feet, and the last pic was in very clear water at about 5 feet.
As for going through a finding what you like, I don't use video much on mine, so it's easier. I shoot in time lapse mode, with a photo every 2 seconds. I end up deleting A LOT of pics, but it helps get what I want. I keep the camera on a 2-3' dowel, which lets me get up close to my subjects. I shoot with protune on and get as close as I can. I do find that the lens is a little wide a lot of the time, but it's a good trade off for the rest of the camera's capabilities.