For documents and physical delivery, it is usually done at different locations, depending on the location of the ship. The final control of the underwater parts is in the dry dock of the port of delivery. In order to obtain the safety quality certificate, the surveyor of the classification society shall carry out a measurement of the bottom of the ship and the underwater parts. The expert may make recommendations for the repair of the vessel that affect the seller`s costs prior to delivery. Sometimes the buyer may appoint his own surveyor, who must be authorized by the classification society to perform the underwater inspection while the ship is on alot. In principle, the seller`s main obligation is to deliver the ship in accordance with the contractual conditions and guarantees. The delivery date may or may not be an essential element of the contract, depending on the contractual clause. .