Opposite margins are an often overlooked relief option for lateral water hazards. It is the equidistant point from the hole where the ball last crossed the margin of the lateral water hazard on the opposite side of the hazard. This point sometimes proves to be a much better angle for the player playing to the hole and allows him to avoid having to negotiate the hazard.
The 5th hole at the Memorial Tournament, is a 527 yard par 5. Players usually take on the hole by going for the green on their 2nd shots. With water fronting the green, the opposite margin option occasionally will come into play.
Estimating the opposite side of a lateral water hazard can sometimes be a time consuming ordeal for an official and the player. Taking added time trying to estimate the equidistant point can ultimately cause pace of play problems.
As an official, it is good practice to get ahead of the lead group and measure a midpoint on both sides of the hazard. Knowing a starting point to pace from will save the official valuable time and provide an accurate measurement in finding the opposite margin.