Warranties are important to ship builders and to those who choose to purchase a vessel directly from a builder, or rely on the services of a naval architect. Express warranties are affirmations of fact made by the seller or any description of the goods that constitutes the basis of a deal between seller and purchaser and which are normally contained in the written contract. The implied warranty of merchantability in essence assures that the goods are up to the standards of the trade and are fit for the ordinary purpose for which they are to be used. The warranty of fitness for a particular purpose is created when the seller knows the specific purpose which the buyer has for the goods and also knows that the buyer is relying on the seller's skill and judgement to provide goods suitable for that purpose or use. A bill of sale is a document which actually transfers title to the vessel.
States have special forms for the sale of a vessel.
The Coast Guard also has its own form and only that federal form may be used to document a vessel with the Coast Guard. A purchase order is a contract normally used for the purchase from manufacturers or for the special order of a vessel. It normally contains provisions for limitation of liability as well as inventories of items included. Given the large sums involved in the purchase of a large commercial vessel, central to the transaction is the ship mortgage. The Ship Mortgage Act of 1920 conferred maritime lien status to ship mortgages, which meant they became entitled to admiralty jurisdiction.