A home inspector walks a Marathon canal-front lot, looks at the seawall, and writes one word on the report: monitor. No cracks bad enough to flag as urgent, no visible lean, nothing that stops a closing. Both sides read that word as a green light.

It isn't. In Marathon, "monitor" on a seawall built decades ago doesn't mean the wall is fine. It means nobody has started the clock yet on the one process that actually determines what happens if that wall needs work: getting four separate authorities to agree you can fix it.

The Wall Was Built Before the Rules Were

Most of Florida's older seawalls, concrete and steel alike, date back to the state's mid-20th-century development boom, long before the layered permitting system that governs coastal construction today existed. Marathon's canal neighborhoods are no exception. In Key Colony Beach, the small canal-front city that sits just off Marathon and shares its MLS market, local permit expediters describe walls now 50 to 60 years old and past their functional life span, the kind of structure that looks stable from the yard but is quietly aging out of its design window.

That gap between when a wall was built and when today's review process was written is the whole story. A seawall poured in the 1960s or 70s answered to none of the agencies that now have a say in repairing it. When it finally needs work, the age of the wall is almost beside the point. The real question is how long it takes to get permission to touch it.

Four Reviewers, One Wall

Repairing or replacing a seawall or dock anywhere in Marathon, whether the property sits on a canal, in Boot Key Harbor, or along open water near Duck Key or Grassy Key, routes through a stack of approvals rather than a single office:

1. City of Marathon Building Department. Local permits are broken into distinct inspection stages: footings, auger tie-back, wall or cantilever, deck, davit bases, and final. Each stage gets its own scheduled inspection before the next can start. The department requires proof of ownership through the Property Appraiser's office or a warranty deed, and any contractor doing the work has to be licensed in both the City of Marathon and Monroe County.
2. Florida Department of Environmental Protection. An Environmental Resource Permit is typically required for construction touching coastal waters or wetlands.
3. U.S. Army Corps of Engineers. Federal sign-off is standard for work in navigable waters, including most seawall and dock projects.
4. Florida Keys National Marine Sanctuary. This is the step that catches people off guard, and it happens to be headquartered inside Marathon itself. NOAA's sanctuary permitting office lists its correspondence address as a Marathon P.O. box, which means the agency with authority over nearshore construction throughout the entire Keys is, quite literally, a local one.

The Federal Permit Isn't the Finish Line

Here's the part that trips up even attentive buyers and sellers: getting the Army Corps permit does not mean the project is cleared. According to the sanctuary's own guidance, entities that receive an Army Corps nationwide or general permit still have to submit their application materials to the Florida Keys National Marine Sanctuary to determine whether sanctuary authorization is also required. Any construction with the potential to affect coral, including seawall repairs and dock installation, falls into that review. If the site sits near coral or seagrass, the sanctuary will likely also request a benthic resource survey, an added biological assessment that shows up after the federal permit is already in hand, not before.

In other words, a project can clear the agency most people assume is the hardest hurdle and still be weeks away from a green light.

What This Means for Your Closing Timeline

This is where the permitting stack collides with the calendar everyone actually cares about. A standard home inspection contingency period is measured in days. Seawall and dock permitting in Marathon is measured in weeks at best and, in some documented cases, close to a year.

Local permit expediters who work Marathon and Key Colony Beach projects describe a wide range: a boat lift permit turned around in about six weeks in one case, while a seawall, dock, and boat lift package on 12th Street in Key Colony Beach, a project type that typically takes up to twelve months to clear, was completed in about five months with dedicated follow-up. One Marathon-based marine engineering firm reports having managed more than 1,500 dock, seawall, and dredging permits in the area since 1999, working directly with the Corps, FDEP, and the sanctuary on nearly every canal and open-water frontage in the city.

None of that fits inside a typical inspection window. If a seawall issue surfaces during due diligence, the honest answer to "how long until this is fixed" is rarely a number either side can plan a closing around.

For Sellers: Get Ahead of the Clock

With 57 properties on the market across Marathon as of early August 2026, competing listings on canal lots are common enough that a documented, permit-ready seawall is a real point of difference, not just a box to check. If your wall shows any wear, a standalone marine inspection before listing gives you time to start the city and state process on your own timeline instead of a buyer's. Because the City of Marathon requires proof of ownership to open a permit, an owner can begin that paperwork now in a way a buyer cannot until after closing. A permit already submitted, or a benthic survey already completed, is something you can hand to a buyer's attorney instead of a promise.

For Buyers: What "Monitor" Actually Means Here

When a general home inspector flags a seawall for monitoring rather than immediate repair, treat that as a prompt to bring in a marine-specific opinion before your inspection period closes, not after. Ask whether any permits are already open on the property through the city's Permit and Inspection Information portal, since unresolved or expired permits attach to the property, not the prior owner. If a marine contractor does flag real structural concern, structure your response around the permitting timeline rather than a repair estimate alone. A price credit assumes the work can start soon. A four-agency approval process says otherwise.

Frequently Asked Questions

Does a standard home inspection in Marathon cover the seawall? Most general home inspections give the seawall a visual look, checking for obvious cracking or leaning, but they are not a substitute for a marine-specific structural assessment. The two check for different things.

How long does seawall or dock permitting actually take in Marathon? It varies by project and by which agency ends up as the bottleneck. Local permit expediters report ranges from about six weeks for simpler boat lift work to close to a year for full seawall and dock packages, depending on whether a benthic survey or sanctuary review is triggered.

If I already have an Army Corps of Engineers permit, can I start construction? Not automatically. The Florida Keys National Marine Sanctuary requires that Corps-permitted projects still be submitted to its office for a separate determination on whether sanctuary authorization is needed, particularly for work near coral or seagrass.

A seawall doesn't have to be failing to change how a Marathon deal gets structured. It just has to be old enough, and close enough to the water, to put four different offices between an offer and a repair. Working through that timeline before you write or accept an offer, rather than after inspection, is what keeps a canal-front closing on schedule instead of stuck in a queue.

If you're weighing a waterfront purchase or sale in Marathon and want a clear read on what a specific seawall or dock situation means for your timeline, Tiffany Alana can walk through it with you and help you plan the transaction around it, not around a surprise.