1) Alternately 2) Back and forth 3) Back, forth, back, forth 4) Continuously swinging 5) How pendulums move 6) How pendulums swing 7) One way of swinging 8) One way to sway 9) The way ferries go 10) The way ferries travel 11) Way to sway Found on https://www.crosswordclues.com/clue/to-and-fro