When is an FCC License Compulsory?
Flying:
Antime you fly internationally, the FAA requires you to have a General Radio Telephone permit
Sailing:
Anytime you are in a foreign port, vessels 65 feet or over (LOA), and when using SSB.
Amateur Radio:
Only when you use Amateur Radio.
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Radio Communication
Finally, when you are "out there" on the water, you may want (or have) to get in touch with your friends on land. An excellent alternative is your radio, whether Marine Radio or Amateur Radio. You can even send e-mails over Amateur Radio Frequencies, staying in touch that way, and sharing your experiences along the way.
Either option has its strengths and weaknesses, but I stronly recommend taking advantage of both!
There are two frequencies that truly stand out on the amateur radio side:
7268 KHZ (LSB) and 14300KHZ (USB). The former provides a lifeline to sailors along the east-coast (the former from roughly Nova Scotia to Trinidad & Tobago) and the latter across the rest of the planet.
Get at least your "General" Amateur Radio license, so you can communicate over long distances; morse code is NOT required.
These "nets" that take place are extraordinary in the way they let you keep in touch.
(Having said that, get the Restricted Radiotelephone Operators Permit, too, as some countries will insist on at least that license when on "Marine VHF." It is an easy thing to get, and applies equally to FAA licensed pilots flying in non-US airpsace.)