20 min AMRAP:
400m Run/Row/ski/bike (24/20)
25 Double Unders/40 single unders
400m Run
50 Double Unders
400m Run
75 Double Unders
400m Run 
100 Double Unders
....Add 25 Double Unders/40 single unders each rounds

PureFit WOD

18min AMRAP:
100m row
40 single unders
200m row
40 single unders
300m row
40 single unders
400m row
40 single unders
....add 100m row each round.