A selection of images of Swans and ducks taken at Cosmeston Lakes in South Wales, all on my Nikon D5200 using either 50mm Nikkor 1:1.4 or 35mm Nikkor DX 1:1.8. That should probably tell you how close I managed to get to these guys, they were really friendly, surprisingly for swans.
50mm, ISO 400, f8, 1/3200th sec. 50mm, ISO 400, f8, 1/2000th sec. 50mm, ISO 400, f8, 1/4000th sec. 35mm, ISO 400, f2, 1/4000th sec. 35mm, ISO 160, f2.8, 1/2000th sec. 35mm, ISO 160, f4, 1/500th sec.