“…like a ship, clean and trim on a dirty sea of pox and camel-dung.”

Where Lies the Land, l. 1 (1806).

This saying appears to be due to John Augustus Shedd; it was quoted in "Grace Hopper : The Youthful Teacher of Us All" by Henry S. Tropp in Abacus Vol. 2, Issue 1 (Fall 1984) ISSN 0724-6722 . She did repeat this saying on multiple occasions, but she called it "a motto that has stuck with me" and did not claim coinage. Additional variations and citations may be found at Quote Investigator http://quoteinvestigator.com/2013/12/09/safe-harbor/
Misattributed

"She must have three square-rigged masts, sir," they told him kindly, "and a bowsprit; and the masts must be in three - lower, top and topgallant - for we never call a polacre a ship."
Master and Commander (1970)

January 1979.
Catch For Us The Foxes (2004)

To My Lord of Falkland.
Poetical Works of Edmund Waller and Sir John Denham (1857)

Lady Wentworth.
Bartlett's Familiar Quotations, 10th ed. (1919)

Source: The Hippopotamus

Introductio ad prudentiam: Part II (1727), Gnomologia (1732)

Source: The Bell