I personally would not worry about human activity affecting the fish much but I'm no expert. I have been scuba diving quite a bit in fresh water years ago (nearly all my diving now is in salt water except for what I do in my pond) and fish in general are very curious. They will scare off from human activity, but after a while curiosity gets the better of them and they will come around to check out what is going on in their territory. They keep their distance as long as activity is going on, but as soon as you are still for a while they come around to investigate.
I also would not worry about sunscreen. The tiny amount in the amount of water is negligible.
Here are some of my main threads about various pond aspects I've been involved with.
Introduction thread and ongoing info about my main 3 acre pond Building a forage pond Building a sediment pond Green Sunfish and bullhead problem in my old pond Refurbishing my son's old dried up pond More than you ever wanted to know.
Don't feel the least bit obligated to read all those, but they are there if you are interested.
If you get down in this neck of the woods and would like to, drop me a private message and if you have time stop by and I'll give you the nickel tour.
