Local Notice to Mariners

The Coast Guard’s Local Notice to Mariners can help you steer clear of new navigation hazards.
Large boat shooting out water
The Coast Guard’s Local Notice to Mariners can help you steer clear of new navigation hazards. Courtesy Shutterstock

On August 16, 2020, while fishing alone in Los Angeles Harbor near San Pedro, California, my friend Dave Brown glimpsed a mysterious object gliding through the water. He recorded a six-second video before it disappeared behind a jetty.

Perplexed and a tad spooked, Brown posted the video on Facebook and asked if anybody might recognize the mastlike object protruding 6 feet above the surface and moving at about 5 mph. I pegged it almost immediately, though I had never previously eyeballed one.

That’s because I’m a boating nerd. I subscribe to weekly emails from the United States Coast Guard, District 11, each containing a link to the Local Notice to Mariners (LNM) on the Coast Guard’s website. I look for notices in areas where I frequently boat, including the waters off San Pedro.


So, when Brown’s post appeared, it jogged my memory. A week earlier, an LNM contained information under the heading “Boeing XLUUV Operations.” It read: “Boeing is conducting engineering sea trials for an extra-large unmanned undersea vehicle called Echo Voyager in the vicinity of the San Pedro Channel and Santa Catalina Island until 10 Oct. 20.” A quick internet search for the Echo Voyager confirmed that the shape of the mast matched the one in Brown’s video.

The notice listed coordinates for the areas of operation and requested that boaters transit with caution and keep 500 yards distance from the Echo Voyager. Though Brown did not spot any other vessels, the notice indicated that two escort boats would be on the scene monitoring Channel 16.

Mystery solved. But there’s a lesson here: Navigational hazards can appear unexpectedly. In the case of the Echo Voyager, the mast is one hazard, but lurking a few feet below the surface is another—the 51-foot hull with a 16,000-pound displacement.


It pays to be aware, and reviewing the weekly Coast Guard LNM for your district is one of the best ways. At you’ll find an LNM link at the top of the page that opens a district map with links to current notices as well as past LNMs.

An LNM might seem overwhelming. For example, for the 29th week of 2021 (the latest as this was written), the District 11 LNM spanned 20 pages, plus another 25 pages of supporting documents. I’ve seen some 60-plus-page LNMs.

Read Next: How to Survive a Boating Emergency


I don’t read it all. Instead, I scan for information relevant to my home waters. The Coast Guard makes this easy by listing notices according to state or region, waterway and locale, except for some general notices. For example, the LNM for District 7 covers Florida, Georgia and South Carolina, but if you boat on the west coast of Florida, you can largely ignore the headings labeled Georgia and South Carolina, unless you’re planning a visit. Further, you can probably skip notices for Florida’s Atlantic coast.

All sections are important, but my favorite weekly read is Section VII, which lists information of general concern such as ongoing dredging operations, bridge construction, harbor projects, buoy deployment, bathymetric surveys, artificial-reef construction and sea trials of mysterious unmanned subs.

Know Before You Head Out

Here are the eight sections of the Local Notice to Mariners, with a brief summary of each. The Coast Guard relies on a plethora of acronyms in its notices, so check the abbreviation legend in the LNM for meanings of those that are not clear.


Section I: Special Notices

Information of special concern to mariners.

Section II: Discrepancies

Reported and corrected discrepancies related to aids to navigation (ATONs).

Section III: Temporary Changes

Temporary changes and corrections to ATONs for dredging, testing, evaluation or marking an obstruction.

Section IV: Chart


Corrections to federal and privately maintained ATONs, as well as National Ocean Service corrections.

Section V: Advance Notices

Advance notice of approved and upcoming projects, as well as related changes to ATONs.

Section VI: Proposed Changes

Notice of proposed but nonapproved projects for public comment.

Section VII: General

Information of general concern to mariners, who are advised to use caution when transiting the affected areas.

Section VIII: List of Light Corrections

A list of corrections to lights on ATONs.