A computational fluid dynamics (CFD) based analysis of the propulsive forces generated by two distinct styles of arm-pulls in front-crawl as well as backstroke is presented in this Technical Brief. Realistic models of the arm pulling through water are created by combining underwater video footage and laser-scans of an arm with computer animation. The contributions of drag and lift forces on the arm to thrust are computed from CFD, and it is found that lift forces provide a dominant contribution to thrust for all the arm-pull styles examined. However, contrary to accepted notions in swimming, pronounced sculling (lateral motion) not only does not increase the contribution of lift forces on the hand to overall thrust, it decreases the contribution of drag forces to thrust. Consequently, pronounced sculling seems to reduce the effectiveness of the arm-pull.