Here’s a good set to help practice spotting the buoy during race day.
If you are training in a 25 yard/meter pool:
Swim 4-6 x 100 yard/meters freestyle. In the middle of each length, lift your head and take 2 arm cycles with you chin on the water. Place your face back in the water and complete the length.
Take 20-30 seconds rest between each 100. Adjust this if you are swimming in a 50 meter pool or in open water.
Here’s the important thing to remember. Each time you finish swimming with your face out of the water, be sure that you return to the correct body position. Lifting your head can cause you to lose a well-balanced body position.