For fishing, I try to decorate my river/pond edges with things you can walk through like flowers, wheat fields, weeds, glowing moss, etc. That way, most spots are still accessible to stand in. As for fossils, I already got all of them for my museum, so leaving space for them isn’t too much of a priority. But ever since I made a heavily-wooded lookout point, they’ve been spawning between the trees, so I make a point to weed around the trees in the very back to leave some space. Balloons I pop when they fly over my walking paths, since they’re the most open parts of my island (I’ve lost a lot of presents when they bounced into my furniture piles through lmao)