Like can I just jump in my boat and go? Do I have to alert any authority about my trip? What are the chances the coast guard boards my boat to search it? How do you find a marina in Mexico? Do I have to alert the Mexican government of my trip? I assume I need a passport.
This is to settle a very polite heated discussion between my partner and I. Where neither of us know what we’re talking about.
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
Another link that has some of the same info as above. But also includes info about re-entering the US. There seems to be an app, CBP ROAM app, for US customs.
https://aglyachtsales.com/what-you-need-to-know-about-visiting-mexico-by-private-boat/
Awesome this along with skycatcher’s link seems to be the right answer.
I’ll admit that it’s slightly more involved than we thought it would be. My partner was of the opinion that the all knowing coast guard would swarm your boat as soon as you hit American waters. I figured it was more likely that if they see you they just come talk to you, but of course the answer is an app.