Looking for something else, I found an article about the Stone Fleet. Have you ever heard of it?

During the Civil War, old ships were filled with rocks and sand, sent south and sunk to block supplies and Confederate ships. Their remains are in Skull Creek and perhaps other areas around Hilton Head Island.

During the Civil War, the Union Navy loaded aging whaleships with rocks and towed them south from New England to coastal Georgia and South Carolina.

There the boats were sunk to block key waterways and frustrate blockade runners, small boats designed to elude Union ships and deliver cargo to Confederate states.

Divers work to learn story of sunken Civil War ships
Stephen Fastenau, The Island Packet of Hilton Head Apr 30, 2017
https://www.aikenstandard.com/news/divers-work-to-learn-story-of-sunken-civil-war-ships/article_a043e954-2df4-11e7-9aa5-2793a2b03973.html

A team of underwater archaeologists, yes underwater archaeologists, from the University of South Carolina Institute of Archaeology and Anthropology mounted an expedition looking for evidence of the ships.

They investigated one of the stone ships that was sunk in Skull Creek. Divers can see a large pile of stones where the ships was sunk. The divers with the University of South Carolina Institute of Archaeology and Anthropology found small pieces of copper. They plan to look further. Perhaps there is more evidence of the ship under the silt.

I don’t know what ship it could have been. I am guessing it is Marcia.

The bark Marcia, destined for the second Stone Fleet off Charleston Harbor also wrecked on the Port Royal Sound shoals.

The  Port  Royal  Sound  Survey,  Phase  One:  Preliminary  Investigations  of  Intertidal  and  Submerged  Cultural  Resources  in  Port  Royal  Sound,  Beaufort  County,  South  Carolina
http://www.artsandsciences.sc.edu/sciaa/mrd/sites/sc.edu.sciaa.mrd/files/attachments/PortRoyalSurvey.pdf

The Port  Royal  Sound  Survey also found remains of two other ships that were headed to Charleston, the Edward and the India, that were lashed together and moored in the middle of Stations Creek off Skull Creek to be used as a machine shop.

Samuel Francis DuPont

The Stone Fleet was under the direction of Samuel Francis DuPont commanding the South Atlantic Blockading Squadron. He was the only member of his family to use a capital D in his name. Later, Du Pont command the first armored “ironclad” ships.

Dupont Circle in Washington, D.C., where Massachusetts Avenue, Connecticut Avenue, New Hampshire Avenue, P Street, and 19th Street NW intersect is named after him. There was a statue of him there, but now there is a fountain.  The statue was moved to Rockford Park in Wilmington, Delaware.

Old Whaling Ships

Gideon Welles, President Lincoln’s Secretary of the Navy, oversaw the purchase of at least 45 old whaling ships. Whale oil had been replaced by petroleum, with its lower labor costs. Old whaling ships could be had relatively cheaply. The ships were rigged to sink. Holes were drilled and temporarily plugged and the ships were filled with stones, dirt, sand and other debris. The ships were sailed south, then sunk to clog shipping lanes to try to keep the Confederacy from importing weapons or anything else they needed.

The first 25 stone ships headed south in 1861, the same year the North took Port Royal Sound and occupied Fort Walker and Fort Beauregard.

In December that year, 1861, Herman Melville wrote a poem about the Stone Fleet.

Stone Fleet

I have a feeling for those ships,
Each worn and ancient one,
With great bluff bows, and broad in the beam
Ay, it was unkindly done.
But so they serve the Obsolete—
Even so, Stone Fleet!

You’ll say I’m doting; do but think
I scudded round the Horn in one—
The Tenedos, a glorious
Good old craft as ever run—
Sunk (how all unmeet!)
With the Old Stone Fleet.

An India ship of fame was she,
Spices and shawls and fans she bore;
A whaler when her wrinkles came—
Turned off! till, spent and poor,
Her bones were sold (escheat)!
Ah! Stone Fleet.

Four were erst patrician keels
(Names attest what families be),
The Kensington, and Richmond too,
Leonidas, and Lee:
But now they have their seat
With the Old Stone Fleet.

To scuttle them‐a pirate deed—
Sack them, and dismast;
They sunk so slow, they died so hard,
But gurgling dropped at last.
Their ghosts in gales repeat
Woe’s us. Stone Fleet!

And all for naught. The waters pass—
Currents will have their way;
Nature is nobody’s ally; ’tis well;
The harbor is bettered‐will stay.
A failure, and complete,
Was your Old Stone Fleet.

The Stone Fleet , Herman Melville

The Tenedos, the ship Melville “scudded round the Horn in,” left New England filled with granite blocks and was sunk in the channel to Charleston the month he wrote the poem.