In periods of reduced visibility, what equipment is essential to signal the vessel operator's intentions or position?

The answer is sound signal. Sound signals like whistles, horns, bells, and gongs, are essential whenever a vessel operator needs to signal his intentions or position such as when meeting head-on, crossing, or overtaking, and in emergency situations in periods of reduced visibility, for instance, fog and heavy rain.

Atp is is our little "pocket" of energy. of course, if you have too little, then it means you have too little energy, and you'll pass out. the way to not have enough, is to have no energy sources (glucose, fats, proteins). you can't have too many atp molecules. cycles like the krebs cycle produce it, but if you have too much of any substrate (or too little for that matter), the cycle stops and atp is no longer made (it stops until substrate levels are such that the process can go on). in any case, this is unlikely since atp is constantly hydrolyzed and remade, even while you're asleep. you won't have too much. if you have zero, you are dead or dying.