Out in the blue water there are some monsters in the deep. They'll take you down into their realm, for a human meaning death. They'll test your endurance, your ability to cope with the cold and sea-sickening rocking in which even the old salts will put down their glass of rum and start staring at the horizon.
I've had a lot of experience in this realm, mostly when I was younger, chasing the leviathan through the waters a hundred miles offshore where the canyons begin and the gulf stream meanders its way up into the northeast pushing warmer water towards the shore for the Benny's enjoyment. While not chasing the mammalian leviathan and rather the fish version of the water borne species, particularly Marline, Tuna, Swordfish and Shark the intensity of the pursuit is no different.
I've spent many months at sea both on civilian and military vessels, many months with the time wasting away watching the different permutations of the water, the sun's refractions, the harsh reality that exists in a world where if you are not on that vessel, that home and personal piece of small land, you are dead. In all my years as a surfer I never experienced something as heavy as being at sea in a small boat during a gale. At the very least while surfing there is the sanctuary of land if you can only hold on just a bit longer; in the deep you can't hold on long enough to survive.
And when I hear this song I think of these things. Of men from a time when there was no Gore-Tex, no neoprene or modern technological advances to shield one from the elements. There was only waxed cotton, tweed and wool. Just as George Mallory summited Everest in what we would call traditional shooting tweeds and buy at Orvis or Holland and Holland the men who roamed the seas searching for oil had little creature comforts.
"Off to Sea Once More" is a darker side, though the side we know is dark enough, of being a mariner, a whaler, back when that was the only way to procure the greasy substance worth more than gold. The "Gloucester Sleigh Ride" was fully known and experienced by most, the waking in the morning sans money and clothes, taken by the woman you had laid down with the night before, the hatred that entity which has taken the life of so many of you comrades.
In the end we derive all from the sea, we came from it in the primordial soup, and eventually we return, whether that be from it taking our lives or the disintegration of our corpses and seepage into the water table and eventually flowing into the seas. Whatever the reason we will end up in that realm with the giants who we've challenged in our living lives and in listening to this shanty one feels the terrible dread that existed and made this land what it is today while in its infancy. Gloucester was the Houston or Saudi Arabia of its day, the biggest oil boom town reaching its arms out and granting asylum in its new breasts under cover of safety. Those that chose only found heartache and death, those who did not never knew of the adventure that could possibly lay in front of them. For us those days are over never to be returned, at least we can grab a taste of the dread in this song.