In July 1973, the Dutch naval submarine Zwaardvis, travelling at periscope depth (ie about 17 m below the surface) about 20 miles off the Norwegian coast, suffered the ingress of a large amount of seawater due to the malfunction of a valve mechanism in its periscope system, as a result of which it sank sharply backwards. Quick intervention meant that this downward movement was halted at a depth of 50 m, and converted into upward movement. Having returned to the surface, the Zwaardvis was unable to sail under its own power as a result of some 40 mt seawater in its engine, navigation, and stern rooms. A large amount of its valuable equipment was damaged by the seawater. Following a request for assistance, the tug Haabrand sailed out, attached mooring lines to the Zwaardvis, and towed it into Stavanger, Norway. The Haabrand claimed a salvage reward. The Court of Appeal below held that the Zwaardvis was not in danger. The Haabrand appealed in cassation to the Hoge Raad.

Held: The judgment of the Gerechtshof 's-Gravenhage is annulled. The case is referred to the Gerechtshof Amsterdam for further consideration and decision with due observance of this judgment.

For there to be salvage remuneration, the ship must be in danger at the time the salvage assistance is provided. From the requirement that the salvage assistance must concern a ship in danger, it follows that the danger of the assisted ship must have existed at the time of the assistance. This also follows from the fact that the rules, both of art 552 DCC and of the Salvage Convention 1910, only attach a claim for salvage remuneration to assistance that is provided to ships in danger which has a useful result; for this implies that only that assistance which puts the assisted ship out of danger, or at least contributes to it, is to be rewarded.

Salvage assistance by a ship or its crew can only be deemed to exist if the ship or its crew provide services as a result of which the ship in distress is rendered safe, or at least contributes towards such safety. To that end, the assisting ship or its crew will have to be in such a position in relation to the assisted ship that they are able to perform those services. This does not prevent the time, effort, and expense involved in reaching that position from being taken into account when determining the salvage remuneration.

In light of the above, the Court of Appeal's opinion that the sailing of the Haabrand to the Zwaardvis cannot in itself be regarded as assistance to the Zwaardvis does not demonstrate that it erred in law. The fact that the Haabrand set sail at the request of the Zwaardvis, and that it attached itself to the Zwaardvis with the consent of the commander of the Zwaardvis and towed the Zwaardvis to Stavanger, does not in itself mean that the Court's judgment is incorrect.

Nor did the Court of Appeal err in law by determining, in order to answer the question whether the Zwaardvis was in danger at the time the Haabrand threw a line to it, whether the Zwaardvis was able to extricate itself from the danger situation under its own power, also in view of the weather forecast and its position in relation to the coast, by taking relevant measures on board.

However, in finding that at the time the line was thrown, the Zwaardvis would be able to sail on its battery power again within a few hours, and subsequently reach Stavanger at a speed of 4 mph, yet failing to take into account that at the time of connecting, the Zwaardvis would have drifted further away from Stavanger under the influence of a moderate to fairly strong wind, nor (in connection therewith) the number of hours needed to get the battery 'up to speed' again, the Court of Appeal (also in view of the State's contention that a higher speed was possible, but would require more energy, and that this would have made reaching Stavanger uncertain) did not provide any insight into its reasoning leading to its finding that the Zwaardvis would be able to cover the (now increased) distance to Stavanger under its own power, and that it was therefore not in danger at the time of connecting.

Furthermore, the Court of Appeal should not have left open the correctness of the Haabrand's assertion that the Zwaardvis sailing at 4 mph could not be steered properly. After all, the correctness of that assumption is essential to the Court's aforementioned conclusion.

If, with regard to the equipment which came into contact with seawater, there was an opportunity to eliminate or limit the harmful effects of that contact, the risk of that opportunity being lost also constitutes a danger to the equipment.