Standing lumbar rotation/flexion DR (Trunk rotation/flexion, drag resisted, cross-body crunch, standing)

Stand up straight with the water at chest depth.
Place your hands beside your head with your elbows bent.
Quickly lift up one leg, bending at your knee and hip, while simultaneously pulling your opposite elbow towards your knee, rotating from your waist.
Return to the start position and repeat with the other side.