In very simple fee amatuer layman's terms. When you sail from the USVI to the BVI for a short transient period of time. You only must declare the stuff you are taking off of the boat. The boat and stuff in it that will stay with the boat and return to the VI does not need to be declared. Anything illegal must always be declared and handled according to the local laws of the county you are transiting through. If you had a case of booze or tv to gift someone on land in the BVI you would need to declare that. When you take a water taxi the intent is clear to take the stuff off the boat onto land. Customs has a right to inspect that. Customs has a right to inspect your entire boat for illegal contraband. You do not and would not owe duty on the boat of its contents when you are a short term visiting transient yachtman. Just like a ship. Pay duty on what comes off. No duty on what stays on the boat. Separate and quarantine anything that may be illegal in the territory your are transiting through(e.g. leave the firearms at home) .