Pathfinder question:

Is Eschew Materials considered a Metamagic Feat?

Yes Lucky.

Kerim, if it's not under the Metamagic section in the SRD, then it isn't metamagic feat.

Generally, it'd be just based off of how much weight it needs to pull, so just encumbrance.

Yep!

Can you have more specific on the swim? What kind of roll or check to keep someone above water?

Whatever swim check you're using to keep yourself above water, accounting for the weight of the rescuee and their possession in your encumbrance calculations which may result in a penalty (or an increased penalty if you were already subject to one) on your roll.

edit: or at least that's my interpretation of what the previous responder meant

Thanks, that makes more sense. So a 17 STR with a swim speed would be at a +2 (-6 for heavy encumbrance, +8 swim speed for swim check) and the ability to take 10.

Question: what would be a normal DC for the swim check itself for swimming in open water encumbered?

17 Str is +3
Having a swim speed provides a +8
the level of encumbrance is unknown, given the lack of information on the rescuee and their gear, but encumbrance penalties to swim checks are doubled, so the total modifier is +11, +5, or -1, depending
the DC is based on the motion of the water, being 10 for effectively still water, 15 for rough water, and 20 for stormy water

Are there any rules in D&D4e for using an arrow as a last resort melee weapon?

Or is it one of those things the DM rules on the spot?

Manifesting a power. Is it possible to hide a manifestation? What's the DC if so? Is it possible to make it seem like something else?