There is not much cooking done while diving. Cooking is done in electric ovens and boilers, but it is usual to do what work is necessary with these when the boats are charging batteries on the surface. Cooking when submerged uses oxygen, makes smells, and expends battery power, and is discouraged. Cold meals are the rule, and submarine people cannot complain of being underfed, as there is a special supply for them of bottled fruits and other extras to obviate the dangers of illness to men living without exercise or fresh air in such confined quarters. On the whole, the crews keep healthy and fit, but there has been a good deal of illness and also eye-strain among the officers during the war.
I have said that while one officer is on watch at the periscope the others sleep or read. It is remarkable, however, how awake they are to certain sounds or happenings. An officer may take some minutes to rouse when called for his spell on watch, but if instead of the gentle shaking of the messenger he felt a change of inclination of the boat, or a new vibratory note from the motors, or if he felt by the cessation of rolling that the boat was sinking, he would be awake in a flash. The human brain seems to keep one technical department always on watch, and it misses nothing. A boat patrolling in a slight swell keeps up a gentle roll at periscope depth, and all the time one hears the rattle and click of the shafting as the fore and aft hydroplanes are worked to keep her at her depth-line. If, for instance, she meets a stratum of fresh water, she will begin to sink; the hydroplanes will be worked up to "hard-a-rise" and left there, with the boat inclined up and trying to climb. The officer at the periscope will order a tank to be partially emptied and will increase speed on the motors to help her climb up again. As she goes down the rolling will cease, and the silence of the hydroplane shafts, the hum of the motors, and the angle of the boat will tell every sleeper at once exactly what is happening; some of them could probably tell the actual depth the boat had got down to without looking at the gauge. In the same way when on passage on the surface a change of note in the roar of the Diesel engines will wake all hands--it might mean something important. When on the surface, there is one sound which wakes everybody without any exception--and that is the electric alarm horn. It makes a dry blaring noise which is unmistakable, and in view of the fact that it may be the preliminary to the loss of the boat, it interests all hands very intimately. There is always the feeling, especially if it is dark, that the officer on watch may have rung it too late, and that before the boat can be forced under a destroyer stem may come crashing through the pressure hull. A submarine hates being on the surface--at least, a patrol submarine does. She has to come up to recharge her batteries or to "make a passage." It must be reiterated that a submarine is fairly fast and of long radius on the surface, and of slow speed and low capacity submerged. It will be understood that a boat is in an anxious position if she has been diving long and her battery is low when she is near enemy patrols. She has _got_ to come up and charge again, and while charging a low battery she is rather helpless. Every weapon has its weak point, and a knowledge of where the weakness lies means a chance to the opponent.