This is a great technique to use as waves on water or for beach scene cakes! For water, use blue colored icing — or try a two-tone look using blue and white icing in the same bag.
Buttercream icing (medium consistency)
Fit the decorating bag with tip 16 and fill 1/2 full with medium consistency icing. Hold the bag at a 45° angle at 3:00 (9:00 for left-handers). Hold the tip slightly above the surface.
For right-handers: Squeezing out icing with even pressure, curve tip down and around to the right as if writing a "c".
Left-handers will pipe reverse c's (like a comma shape) by following same procedure as above, just curving tip down around to the left.
Repeat to complete the border, using a steady, even pressure.
To end, stop pressure, pull tip away.