i believe that the niose made in the boat,such as,dropping things, livewell door closed hard,just any kind of bings and bangs can scare fish.i think the sound waves carry thur the water off of the boat.i don't think talking and laughing spook the fish.i was fishing the other day,and was reeling in to check my bait(got to check your bait folks)i was using a 1/2 oz. sinker it hit the side of the boat(not hard)and it still sounded like a 22cal.went off in the boat.i'm sure it sent sound waves out from the boat.so,yes i believe some sounds can affect the fish.i think the release of smaller fish, if done gently,will not spook fish.the fish splashing is a natural sound for them.this is my opinion,nothing here scienitific.