Hmm, most of our PCs fear water and for good reason.
Lets say that you fall off a log and end up in a swift flowing river.
You are wearing a breastplate and have an additional 20 pounds of gear. Lets say you took one point in swimming so you could take 10 in calm water.
This is not calm water. The DC is 15 and your effective swim skill is -9. If you wanted to lighten your load you could drop everything and your effective skill would still be at -5. You are dead, you just don't know it yet.
If you fail your swimming check, you must make another check or you go under. Every round under water is an additional -1 to your swimming skill. Even if you make your roll, you still taking 1d3 subdual damage (or 1d6 real damage if rocks are involved).
You really need to get out of that armor, but it is going to take you ten rounds to do it. You are going to be 10 rounds down on your breath timer and at -10 to your swimming skill from your time under water.
Happy swimming.
Astlin