I just finished reading
Silent Running by James Calvert where he talks about patrolling in the USS Jack in the South China Sea:
By running on the surface and setting a watch on the high periscope, we achieved a significant increase in our coverage. In this condition we had an effective height of eye of fifty feet ... we could see the top of a ship at fifteen miles, her smoke even farther. Thus we were covering an area of more than seven hundred square miles with the high periscope watch, as compared to a maximum of fifty square miles with the submerged periscope watch.
Crew members volunteered for this watch because there was a pool rewarding the first member to spot a target!
I guess our lookouts are getting some feedback from the volunteers in the conning tower!