Needs to be done on the Infinity Pool level.
There should be a golf ball somewhere in the Pool area.
Wait for one of the non-floating Duckys, like the Stone or the Metal one. Press "Tab" until your camera is focussed on the Ducky and use the scrollwheel to zoom in on the golf ball.
Camera has to be fairly close to the golf ball for the Achievement to unlock. Depending on the position of the Ducky, you might need to wait for a different one with a better position.