Flat water and slow-moving water
Also: ZW, calm water, still water
Slow-moving water means flowing water without any notable whitewater, flat water means still water such as lakes.
Slow-moving water is ideal for beginners, but not automatically harmless: weirs, fallen trees, bridge piers and floods exist on calm rivers too. On large lakes, wind and waves are the biggest dangers.
Where whitewater begins is described by the difficulty scale.
