For open water swimmers, being able to sight efficiently in the water, is not only vital from a navigational perspective, but also to minimise drag. The higher we elevate our upper bodies to sight above the water line, the more we will lower our hips - causing our legs to drag in the water behind us. In order to sight efficiently, we are ideally looking to only elevate our eyes above the water line for as short a time as necessary to view the next focal point (a turning buoy for example).
In the video below, you will find 3 different methods for sighting in the open water. There is no absolute right or wrong way that applies to every swimmer. The correct way for you to do it, is the method that allows you to sight as clearly as possible with the minimum amount of drag. However, if possible, I would encourage you to at least attempt to become comfortable with either of the techniques that involve breathing - as these will likely result in less disruption to your normal swimming stroke.
Even if you believe you are following a set of feet that are navigating well, I would still recommend sighting regularly. When sighting with a breath, I suggest every 4th or 6th stroke when breathing on one side only, or 3rd or 5th stroke when breathing bilaterally. If you are sighting in between breathing strokes, I would recommend sighting on every non-breathing cycle.
Simple sight with no breath (0:54)
Sight into breath (1:37)
Breath into sight (2:37)