The OP and the USCG book have both apparently fallen for the
marketing hype and vague semantics of the builders.
Technically, "seaworthy" was a legal term used by the
insurance consortiums of LLoyds and virtually any vessel can be "seaworthy" as the term refers to a specific purpose (voyage) and through history has included crew's qualifications, spares, and consumables onboard and appropriate to that specific voyage.
i.e. She might be a "safe" vessel but not "seaworthy" in the hands of an incapable crew or
captain and without sufficient
food onboard for that specific voyage with that specific crew.
There is a long history of legal issues involving "seaworthiness" that has little to do with how the word is used on this or any other forum.
much like the word "trawler"
Article III
Rule 1 of the Hague-Visby Rules provides: "The carrier shall be bound before and at the beginning of the voyage to exercise due diligence to— (a) Make the ship
seaworthy. (b) Properly man, equip and supply the ship. (c) Make the holds, refrigerating and cool chambers, and all other
parts of the ship in which goods are carried, fit and safe for their
reception, carriage and preservation.
Section 3 of the Carriage of Goods by Sea Act 1971 adds: " There shall not be implied in any
contract for the carriage of goods by sea to which the Rules apply by virtue of this Act any absolute undertaking by the carrier of the goods to provide a
seaworthy ship." This provision makes it clear that there is no strict liability to provide a seaworthy ship.
McFadden v Blue Star Line (1905)[1] provides that: "A vessel must have that degree of fitness which an ordinary careful and prudent owner would require his vessel to have at the commencement of her voyage having regard to all the probable circumstances of it…Would a prudent owner have required that it (i.e. the defect) should be made good before sending his ship to sea, had he known of it? If he would, the ship was not seaworthy…" [2]
Together with the Hague Visby Rules, the common law provides that the
concept of "seaworthiness" covers: the ship, its
equipment and supplies,[3][4] the crew,[5] the vessel's suitability for the particular cargo [6] and its suitability for the particular voyage or for particular
ports.[7][8]
The Rotterdam Rules, which are intended to replace the Hague Rules, Hague-Visby Rules and Hamburg Rules, are many years away from ratification. If and when the Rotterdam Rules come into force, the carrier will have to maintain seaworthiness throughout the voyage, not just at the start. Presumably the standard of seaworthiness at sea would be somewhat lower than when in port (where
refit facilities are available).[9]