Bernard -
I never stood watch on a U-boat, but I stood enough watches on surface ships to have some idea of what it must have been like. Even when the weather was good, sunburn and eyestrain were a problem. Here is an exercise which might give you a perspective. Find an unshaded ocean or lakeside vantage point, and stand there (you can lean against a fence or rock, but don't recline, and never sit) for four hours looking out over the water (never back toward shore or along adjoining beaches.) If the vantage point looks eastward, choose the first four hours of daylight -- if westward try the last four hours of daylight. If you have a pair of binoculars, force yourself to identify every bird and airplane which becomes visible and estimate its course. If an incoming bird or plane is close enough for you to make that identification immediately, imagine the wrath of your boss if you carelessly set your workplace afire.

Enjoy the fresh air and sunrise or sunset. =AL=