For a commercial vessel, if you want to carry cargo from one US port to another. See https://en.wikipedia.org/wiki/Merchant_Marine_Act_of_1920 https://en.wikip

For a commercial vessel, if you want to carry cargo from one US port to another. See https://en.wikipedia.org/wiki/Merchant_Marine_Act_of_1920 https://en.wikipedia.org/wiki/Merchant_Marine_Act_of_1920 though that also requires the vessel to be US-built/owned/crewed...