GX.Sigma
Adventurer
Wall of Force into water:
If you're thinking about it in terms of world physics: The SRD says that the wall fails unless it is continuous and unbroken when it is formed. Since you're trying to evoke it into a volume that the water already occupies, I'd say it fails. (In other words, it can't push water out of the way to make room for itself.)
Temporary hit points:
Say you're at 0 hp, you're unconscious, and you're dying. If you get temporary hp, then you're still at 0 (real) hp, still unconscious, and still dying, and you have some temporary hp.
If you're thinking about it in terms of world physics: The SRD says that the wall fails unless it is continuous and unbroken when it is formed. Since you're trying to evoke it into a volume that the water already occupies, I'd say it fails. (In other words, it can't push water out of the way to make room for itself.)
Temporary hit points:
Say you're at 0 hp, you're unconscious, and you're dying. If you get temporary hp, then you're still at 0 (real) hp, still unconscious, and still dying, and you have some temporary hp.