The original tune is "Farewell and Adieu to You Spanish Ladies", which shows up as early as 1769 (in a journal of the Nellie). Melville references the song and others in his 1850 novel White-Jacket. Upon deeper inspection this poem is full of images of uncertainty, fear, and peril (unlike the typical rendition of Spanish Ladies). Traveling the coasts of England, the song's narrator is far from rounding the Cape of Good Hope, unless we take that too as a metaphor.
A Deadlight is a nautical term for a piece of heavy glass set into a deck or ship's side to allow light.
The Deadman (or Deadman's Point), is today known as Dodman Point on the south Cornwall coast, near Plymouth.
The Sargasso sea is the bulk of the Atlantic ocean just east of mainland North America.
The Doldrums is "a popular nautical term that refers to the belt around the Earth near the equator where sailing ships sometimes get stuck on windless waters." Now known for periods of boredom or depression.
The Flying Dutchman is the legendary ship of Dutch captain Van der Decken, condemned to cruise forever off the Cape of Good Hope (ill luck).
A flipper as in "tipping your flipper" (waving) must just mean "hand"
A goney or gooney is another name for the albatross, a sea bird. One of the few companions a lonely sailing crew has.
Farewell and adieu to you noble hearties,—
Farewell and adieu to you ladies of Spain,
For I've received orders for to sail for the Deadman,
But hope with the grand fleet to see you again.
I have hove my ship to, with main-top-sail aback, boys;
I have hove my ship to, for to strike soundings clear—
The black scud a'flying; but, by God's blessing, dam' me,
Right up the Channel for the Deadman I'll steer.
I have worried through the waters that are called the Doldrums,
And growled at Sargasso that clogs while ye grope—
Blast my eyes, but the light-ship is hid by the mist, lads:—
Flying Dutchman—odds bobbs—off the Cape of Good Hope!
But what's this I feel that is fanning my cheek, Matt?
The white goney's wing?—how she rolls!—'t is the Cape!
Give my kit to the mess, Jock, for kin none is mine, none;
And tell Holy Joe to avast with the crape.
Dead reckoning, says Joe, it won't do to go by;
But they doused all the glims, Matt, in sky t' other night.
Dead reckoning is good for to sail for the Deadman;
And Tom Deadlight he thinks it may reckon near right.
The signal!—it streams for the grand fleet to anchor.
The captains—the trumpets—the hullabaloo!
Stand by for blue-blazes, and mind your shank-painters,
For the Lord High Admiral, he's squinting at you!
But give me my tot, Matt, before I roll over;
Jock, let's have your flipper, it's good for to feel;
And don't sew me up without baccy in mouth, boys,
And don't blubber like lubbers when I turn up my keel.