I pretty much agree with what everyone here says, but I'm a classic, do as I say not as I do.

1) My "water" knife is a fully serrated Atlantic Salt by Spyderco. I've never used it to cut a line in an emergency but I think it would excel at it. I can verify that it cuts french bread and cheese quite well though.

2) I'd prefer a plain edge blade for pretty much everything else.

3) I actually carry a partially serrated blade 99% of the time. It is on my Skeletool. It has not let me down to date. Apparently the Skeletool I have now comes with a straight blade on it. I wish I had that one, but this seems to work fine.

3a) When I think I might "need a knife" I carry one or several others. The Skeletool is my EDC though.