What does "spinning upon the shoals" mean?
What does the verb spin mean in this poem of Emily Dickinson? The stanza with the line in question is:
Ring—for the Scant Salvation—
Toll—for the bonnie Souls—
Neighbor—and friend—and Bridegroom—
Spinning upon the Shoals—
The research I did suggests that the word shoal means a school of fish, but I am not convinced to such opinion. I think that the words the shoals describe shallow waters in this poem and the verb spin describes people either moving swiftly or floating in these waters.
What do shoals and spinning mean in this poem?
I don't think there is any allusion to shoals of fish here.
In the first stanza, there has been a storm at sea, with four survivors and forty lost, "gone down together into the boiling sand."
The "four" and "forty" are presumably sailors, or ships' passengers, or even the number of ships sunk by the storm or saved from it.
A "shoal" is an area of shallow water. Because of the shallow and uneven depths of water, the currents in such an area are often fast, hard to predict, (the direction changes from point to point as the depth varies) and dangerous.
A ship which gets into difficulty in such a place may be "spun around" by the stormy weather, because the keel of the ship is dragging on the bottom of the water but never becomes stuck fast in one place.
The image of the second stanza is of the bodies and souls of the victims being dragged about for ever as the sea tides wash back and forth over the shoals, rather than being buried "safely" in a grave on land.
You might want to do some research into notorious shoals and sandbanks that are navigation hazards even in fair weather, such as the Goodwin Sands near Dover in the UK, where more than 2000 ships are known to have been wrecked in an area just 10 miles long and 3 miles wide. For example in a single night in 1703, more than 50 ships and 2000 lives were lost in a storm. As the sandy sea bed is continually moved by the sea, sunken ships (and the remains of their crew) are sometimes uncovered after having been buried for many years.
One Lexico (Oxford Dictionaries) definition is
shoal2
NOUN1 An area of shallow water.
we clawed our way out from the Bahamian shoals into the deep waters of the Atlantic1.1 A submerged sandbank visible at low water.
1.2 (usually shoals) A hidden danger or difficulty.
he alone could safely guide them through Hollywood's treacherous shoals
So I think the word was carefully chosen by Emily Dickinson, and spinning suggests that they are not at rest. In the minds of the survivors, they are not, and their physical bodies may still be carried by the tides and currents.
Edit:
The verb to spin has many nuances as shown also in Lexico, too many to reproduce completely here. The meaning of spinning has allusion to fishing, turning, drawing something out, confusing, and so on.
As @FumbleFingers observed, the meaning of poetry is conjured in the mind of its reader, whether or not that was the intention of the writer.
Spin here matches the OED’s sense 7a for that verb:
To move rapidly; to run quickly; now esp. to ride or drive at a rapid and even rate.
Shoals here matches the OED’s sense a for the first of the two shoal nouns:
A place where the water is of little depth; a shallow; a sand-bank or bar.
So spinning upon the shoals here primarily means hurrying along [or amid(st) or among(st)] the shallows.
It just sounds better to say SPINning uPON because of the alliteration, and the syllables fit the scansion better.