You attempt to keep your head above water while swimming or treading water.
Roll+BOD. You gain one instance of favour for each empty hand you have available to paddle or scull.
Complete Success: You stay afloat effortlessly, regardless of water conditions or turbulence, so long as it is physically possible to do so.
Success: You stay afloat in all but the most extreme conditions, such as a hurricane or tsunami.
Partial Success: You stay afloat, but you struggle against the elements. You sink if there are heavy waves or high winds.
Failure: You manage to stay above water only in calm conditions. You begin to sink if there are any waves at all.
Complete Failure: You lose your rhythm and begin to sink immediately.
If you cannot keep yourself from sinking, then you risk drowning.