We rid the lake of 99 mute swans a decade ago. Caught 'em using speedy fishing boats and 10 ft. long rerod that we bent the end into a shepherds crook. Guy in front snagged 'em around the neck at speed with the crook end, they go docile, grab 'em, Duct tape the beak and feet and put 'em in a box, two to a box. They don't fly well in the middle of June.
In the years after that, we'd go to the nests and run off the swans with a long handled broom while the other guy shakes the eggs and drills a small hole, then carefully put back the eggs. By the time the swans figger out the eggs won't hatch, it's too late to lay more. That way we controled the mute swans at about 4.
Mute swans are mean, aggressive and territorial. No way one could make you drown though. Grab it by the neck and kill it. Then use it for bouyancy. Dead guy must have been a wimp.