Frank J. Wilstach, comp. A Dictionary of Similes. 1916.
Undulate
Undulating like the sea.
—Boccaccio
Undulating like diluvian billows fixed into stone in the midst of their stormy swell.
—Edward Bulwer-Lytton
Undulating, like the mane of a lion.
—Alexandre Dumas, père
Undulating like a snake rearing on its tail.
—Théphile Gautier
Long seaweed undulated beneath the water, like the waving of long tresses in the wind.
—Victor Hugo