The cut-offs for size category (based on longest inflexible axis) are~
~3 inches for Nuisance
~6 inches Fine
~1 foot (11.25 inches) for Diminutive
~2 feet (22.5) inches for Tiny
3.75 feet (45 inches) for Small
7.5 feet for Medium
15 feet for Large
30 feet for Huge
60 feet for Gargantuan
125 feet for Colossal
250 feet for Enormous
Useful chart that! Will have to keep a copy of that with my notes.Page 217: Starvation and Thirst
Outside of special circumstances (Like traveling through a desert) I suspect that many groups do not bother with tracking food and water. But, if you want to, here are the rules for it. Your average person needs three meals a day, some species need less though. I note that this does not seem to depend on size, so a Large creature eats the same as a Small one (Or when comparing a drake and a pech the Small character actually eats MORE!) You can go without food for a few days without penalty, but then you have to start making Fort Saves that become harder to make every day and when you fail become Fatigued and suffer increasing amounts of Lethal Damage.
For water you drink a quart a day, two in a desert or other hot conditions. Again, regardless of Size. Unlike food, you cannot miss getting water for even one day or you start making Fort Saves or take penalties, same penalties as with food. And in both cases you cannot lose the Fatigued condition, no matter what you do, until you eat or drink.Page 217: Suffocation
Be it drowning, strangulation, or vacuum exposure, this covers any situation where a character cannot breathe. Obviously, not all situations apply to all characters; while a human would suffer this in water, a fish would suffer this in air. Likewise, some things do not need to breath, like undead. You can go for a few rounds without breathing; the higher your Con the longer you can hold your breath. After that, you have to start making Fort Saves. When failed, a Special Character immediately loses all their Vitality while a Standard falls unconscious. Next round, if they still cannot breathe, a Special Character loses all their Wounds and following that they begin dieing.Page 217: Terminal Situations
This only applies outside of combat. So, you have a situation where, let us use the book's example, that an assassin sneaks in and puts a knife to the throat of a sleeping soldier. Now, from a meta game perspective, that knife does not do much damage compared to what the soldier can take. However, from a narrative and logical perspective it does not matter how much Vitality that soldier has, that assassin can kill him with a quick slash (Provided he cuts the arteries anyway). That is where this rule comes into play. As long as the assassin has the soldier at his mercy he can simply spend one single AD to kill the soldier. The solder gets no Save, he simply dies immediately. The players can either be the victims or the ones with the knives, whatever the situation calls for. This can be useful for the GM, just be careful as to when you use it, and that the victim is truly helpless. I would also assume that the killer could, instead of spending AD, do a Coup de Grace, which does not cost AD, but gives the victim a chance to survive.Page 217: Underwater Combat
If you have poor Athletics then you suffer penalties to Attack, Reflex, and Skill Checks (Other than Swimming) while submerged. Also, bombs have larger blasts underwater.Page 217-218: Vision and Hearing
And also smell. How good you are at seeing, hearing, or smelling things over distance depends on your Wisdom Score. The more Wis you have the farther you can see, hear, and smell effectively. Every increment beyond the first imposes penalties on rolls using these senses, like Notice.
Also on the table on the next page we see how light and noise affect vision and hearing. Light also affects Defense; it is harder to be hit in darkness.
Next time, we get into all the fun things you can do in combat, which is actually quite a nice list.