I’m not an expert whatsoever but I have done a fair bit of international travel and resided overseas for multiple years.

That experience has lead me to believe that unlike many countries the US government doesn’t care to track you leaving the country. They may know incidentally due to other processes such as airport/airplane security checks but those are performed by TSA; not the CBP. Both agencies fall under DHS but perform distinct functions.

When leaving the US by air you will go through security checks, but when arriving you come through customs and immigration.

All that is to say I think when traveling by private boat your main concern will be with entry into Mexico; not departing from the US.

I had long ago fantasized about traveling the world by sailboat and often wondered how immigration via seaport would work but never pursued an answer. Your question motivated me to do so.

This is what I found regarding entering Mexico via seaport from a private boat:

STEP 1: Submit passport of captain and vessel documentation along with $332 fee

STEP 2: Complete form with documentation of passengers and crew

STEP 3: Submit completed form from STEP 2 along with receipt from STEP 1

STEP 4: Await confirmation of approval from STEP 3 and receive entry authorization.

STEP 5: There is no step 5! Enjoy a margarita or paloma on the beach!

https://consulmex.sre.gob.mx/vancouver/images/pdf/boat.pdf

Currently sailing to Mexico. You need to obtain an import permit for your boat into Mexico, even for short time. It's called a Temporary Import Permit, TIP and at today's rate is just under $20. You can ask for it between 11 and 60 days before arrival in Mexico. The application is done online at https://www.banjercito.com.mx/registroVehiculos/# Top right switches to english if needed.

You will need your boat registration (Federal Coast Guard Documentation or State issued Registration) Passport of boat owner

If the boat is owned by an LLC you'll need more ownership proof.

On arrival in Mexico you must contact immigration and customs. You'll need to fill in paperwork and present crew list and crew passports. Declare any alcohol, controlled medication and similar. Until you have sorted this you should fly flag Q, quarantine yellow flag. Once you have been given authorization (clearance) into the country you take Q flag down and replace with a Mexican courtesy flag, flown on Starboard side.

Failure to do the above can land you in major trouble.

passport is bare minimum, but you need to get boat's papers in order. you gotta pay a visit to mexican consulate for that

putting some of these words in search engine of your preference should get you link like this: https://www.boatus.com/expert-advice/expert-advice-archive/2017/april/boaters-guide-to-crossing-the-border or like this https://consulmex.sre.gob.mx/vancouver/images/pdf/boat.pdf

Well you need a passport, even if you're an american citizen. You probably want to know which port you'd be arriving at, and have paperwork ready.

I misread "marina" and thought you were asking about where to find marijuana in Mexico.

The most casually planned smuggling operation in history there.

You'll need a port pass, sailor moon. Otherwise known as a pass port, because you need it to pass through a port.

Those pesky laws of the land really only kick in once you hit land. Until then you're in international waters. Technically you might already be considered to be in Mexico but only the coastguard would argue such a thing until you dock.

In practice, if you just anchor in a bay and row to shore...you might enjoy whatever you came to enjoy and then get all the way home without anyone asking you about anything.

This is good because it saves you dealing with beaurocrats but you also don't get a nice stampo in passporto.

Another option would be to team up with a cartel and shoot your way into Mexico .

No advice to offer but tell us about your trip when you get back that sounds cool as hell.

Yeah you need a passport. Just look up any marina and go there. Coast guard might search your boat, but they can do that to anyone. You don't need to alert either government.

For finding a marina I expect Google Maps would work fine. It will also allow you to measure distance.

Stay on the ocean. If you take the land route, you won’t get five feet.