Nowadays this type of diving would be done using an eCCR (and backup open circuit), where some software on a microcontroller controls the amount of oxygen in a breathing loop. A scrubber (hopefully) removes the CO2. Changing the gas mixture as you go is required to reach these sorts of depths because oxygen becomes toxic at pressure, and gas density itself can cause issues with breathing.

  The legend lives on from the Chippewa on down
  Of the big lake they called Gitche Gumee
  The lake, it is said, never gives up her dead
  When the skies of November turn gloomy

  With a load of iron ore twenty-six thousand tons more
  Than the Edmund Fitzgerald weighed empty
  That good ship and true was a bone to be chewed
  When the gales of November came early
  
  The ship was the pride of the American side
  Coming back from some mill in Wisconsin
  As the big freighters go, it was bigger than most
  With a crew and good captain well seasoned
  Concluding some terms with a couple of steel firms
  When they left fully loaded for Cleveland
  And later that night when the ship's bell rang
  Could it be the north wind they'd been feelin'?
  
  The wind in the wires made a tattle-tale sound
  And a wave broke over the railin'
  And every man knew, as the captain did too
  'Twas the witch of November come stealin'
  The dawn came late and the breakfast had to wait
  When the gales of November came slashin'
  When afternoon came it was freezin' rain
  In the face of a hurricane west wind
  
  When suppertime came the old cook came on deck sayin'
  "Fellas, it's too rough to feed ya"
  At seven P.M. a main hatchway caved in, he said
  "Fellas, it's been good to know ya"
  The captain wired in he had water comin' in
  And the good ship and crew was in peril
  And later that night when his lights went outta sight
  Came the wreck of the Edmund Fitzgerald
  
  Does anyone know where the love of God goes
  When the waves turn the minutes to hours?
  The searchers all say they'd have made Whitefish Bay
  If they'd put fifteen more miles behind her
  They might have split up or they might have capsized
  They may have broke deep and took water
  And all that remains is the faces and the names
  Of the wives and the sons and the daughters
  
  Lake Huron rolls, Superior sings
  In the rooms of her ice-water mansion
  Old Michigan steams like a young man's dreams
  The islands and bays are for sportsmen
  And farther below Lake Ontario
  Takes in what Lake Erie can send her
  And the iron boats go as the mariners all know
  With the gales of November remembered
  
  In a musty old hall in Detroit they prayed
  In the Maritime Sailors' Cathedral
  The church bell chimed till it rang twenty-nine times
  For each man on the Edmund Fitzgerald

  The legend lives on from the Chippewa on down
  Of the big lake they call Gitche Gumee
  Superior, they said, never gives up her dead
  When the gales of November come early

Lake seiches can occur very quickly: on July 13, 1995, a large seiche on Lake Superior caused the water level to fall and then rise again by one metre (three feet) within fifteen minutes, leaving some boats hanging from the docks on their mooring lines when the water retreated

I still remember the "oh I get it" moment when I visited Michigan as a teen and saw Lake Michigan for the first time.

Sadly, the days of getting to walk out onto the locks for "Engineer's Day" (held on the last Friday of June, typically) are over. In 2025 the public wasn't allowed into the operational area of the locks ("out of an abundance of caution").

> they are swept by Borean and dismasting blasts as direful as any that lash the salted wave; they know what shipwrecks are, for out of sight of land, however inland, they have drowned full many a midnight ship with all its shrieking crew.

https://en.wikisource.org/wiki/Page%3AMoby-Dick_(1851)_US_ed...