Movement in water

[Bagpuss]

Also, note that the entry for "none of the above" allows normal movement. Is "failed swim check" the only example of none of the above? If so, why would it list movement as normal?

Unfortunately under the swim skill description it says

If you fail by 4 or less, you make no progress through the water. If you fail by 5 or more, you go underwater.

So if you fail a swim check by 4 or less you make no progress.

If you fail by 5 or more you can move at your normal speed, at least according to the table.

Although I'm sure most DM's will say the only direction you move is straight down.