Click and drag with the mouse to manipulate the "rope". Press F to toggle filling the underside of the rope, turning it into water Press L to toggle locking the mouse's movement to vertical (it sounds confusing - experiment to see what it does) Experiment and play around!
All by me, @Turtle1331 Tip: Turn on filling, set the ratio at 0.8-0.9, make sure lock is off, and drag the mouse to create water waves!