Lifting your head to sight makes your feet drop, which slows you down. Lifting your head quickly (aptly known as “heave” in nautical terms) can also make you seasick, so it is important to keep your head down as much as possible. To minimize heave, lift your eyes first and let your head follow. Let your eyes clear the water but not your mouth. Find your target, then turn your head to the side to breathe.
There are visual points of reference everywhere above the water and below, to the side and behind you: paddlers, kayaks, shoreline and other swimmers. Use them all.
When you must look forward, you need a target that you can find quickly. No matter how big and how orange the buoy is, it will be hard to find. A landmark works if there is one, but you need one for every change of direction on the course. The easiest thing to spot is the crowd of swimmers converging on the buoy. Let them do the sighting work. All you have to do is follow.