white water 
noun [mass noun, often as modifier]
Fast shallow stretches of water in a river: white-water rafting...
- I'm told that the Orchy is also the most thrilling river in Britain for white-water rafting.
- The steep hills and valleys also offer superb rivers for white-water rafting.
- They can go white-water rafting and swimming, and Youth in Action days teach orienteering, map-reading, team-building and first aid.
- run (or take) the risk (or risks)
- run out
- run-out groove
- run out of gas
- run out of steam
- run out on
- run-out table
- run over
- run-producer
- run proof
- run rate
- run resist
- run resistant
- runrig
- run rings round
- run riot
- run-round
- runshie
- run someone in
- run someone out
- run someone out of town
- run someone ragged
- run someone/thing close
- run someone/thing down
- run someone/thing over