There is something about standing at the edge of Lake Michigan — the grey-green water stretching out into a haze that dissolves the horizon, the wind carrying the faint mineral tang of depths no sunlight has ever troubled — that compels a person to ask: what, exactly, is the difference between this and the sea? It is a question the lake itself appears to have grown tired of leaving unanswered.

In what legal scholars are calling an “unprecedented act of hydrological self-advocacy,” Lake Michigan has formally petitioned the U.S. Department of the Interior to be reclassified from “Great Lake” to “ocean,” arguing in a 200-page legal brief that it has “long outgrown the dismissive label of ‘lake’ and deserves recognition commensurate with its majesty.” The filing reads less like a legal document and more like a body of water in the grip of an identity crisis — or perhaps, more charitably, an awakening.

The petition, filed Monday through a team of environmental lawyers based in Hyde Park, cites Lake Michigan’s 22,404 square miles of surface area, its ability to produce waves exceeding 20 feet, and what the brief describes as “a general vibe that is, by any honest assessment, extremely oceanic.” One struggles to argue. The numbers alone carry a certain gravity — 22,404 square miles of restless, wind-torn water, a surface area larger than entire nations where people are born, live full lives, and die without ever seeing its shore.

“When you stand on the shore at Montrose Beach and look out, do you see the other side? No, you do not,” the brief reads. “When a November storm rolls in and capsizes boats, does it feel like a ‘lake’? It does not. Lake Michigan has been living a lie, and it is time for the federal government to acknowledge the truth.”

There is, embedded in that passage, something almost mournful — the quiet anguish of a thing that has always known what it was, waiting for the world to see it clearly.

Dr. Ellen Kirkpatrick, a limnologist at the University of Chicago who was consulted on the petition, says the request isn’t as outlandish as it might seem. “Lake Michigan has currents, tides — tiny ones, but still — and it’s been known to swallow entire ships without a trace. At what point do we stop pretending this is the same category as Lake of the Ozarks?” The swallowing of ships is worth pausing on. There are vessels resting in the silt-dark silence of Michigan’s floor that have not seen light in a century, their hulls slowly becoming part of the geology. The ocean does this. Lakes, in the common imagination, do not.

The Department of the Interior has not yet formally responded to the petition but released a brief statement saying it would “review the filing through established channels.” A source within the department, speaking on condition of anonymity, described the mood as “confused but intrigued.” One suspects the lake has inspired this particular combination of feelings for millennia.

Not everyone is supportive of the reclassification effort. Lake Superior, which has long considered itself the most impressive of the Great Lakes, issued a terse statement through its own legal team calling Lake Michigan’s petition “desperate and frankly embarrassing,” adding that “if any Great Lake deserves ocean status, the answer is obvious, and it isn’t the one with Navy Pier on it.” There is a sibling rivalry among these inland seas that predates human naming conventions — a jostling for supremacy played out in storm surges and depths and the sheer cold indifference of their waters.

Chicago residents, for their part, seem largely in favor. “I’ve always said Lake Michigan is basically an ocean,” said Lincoln Park resident Terrence Walsh, 41, while jogging along the lakefront. “It’s cold, it’s huge, and I once saw a wave knock a full-grown man off the rocks at Promontory Point. That’s ocean behavior.” Walsh jogged on, the lake looming beside him, vast and grey and utterly unconcerned with whatever humanity decided to call it.

The petition is expected to be reviewed over the next 18 months. If approved, Lake Michigan would become the first body of freshwater in U.S. history to hold ocean status, a designation that would entitle it to Coast Guard patrols, NOAA weather monitoring, and — most importantly, according to the brief — “the respect it has always deserved.”

Whether the federal government grants the request or not, the lake will go on doing what it has always done: churning, freezing, thawing, swallowing light whole at dusk, and reminding anyone who stands long enough at its edge that the labels we give to things are small, and the things themselves are not.