They stand a much greater chance of escaping predators if they can fly.
A goose around here lived to the ripe old age of 39. She was half Greylag and flew really well. She survived four husbands, all domestic and killed by predators (red fox) - she'd just fly out of range.
I too would get mad over a neighbors goose in my pool. Heck I get mad when the door doesn't close on the pool screen and one of OUR geese or ducks gets in the pool. As OB said, clip one wing and make sure to have adequate fencing to keep them in.
When I was married, a neighbors ducks would come over and swim in our pool sometimes, I loved that they would come over but husband did not like it lol.