If you have a triathlon or swimming plan you would have noticed there are a lot of two letter acronyms within the swim workouts, this article explains all of them.
CH = Closed Hands (fists)
To complete this drill swim freestyle, but with your hands in a fist.
PU = Pull (buoy between legs)
Your legs will not be in use, but your arms should follow front crawl.
KB = Kickboard (only legs)
Arms out in front holding a kickboard, legs kicking as normal (freestyle).
SA = Single arm (freestyle)
Complete freestyle, but only using one arm. Other arm should be out in front. Change arm every length.
SC = Sculling
Legs kick as normal, however, you move the water in front of you by pushing your arms laterally (in and out).