Whether crabs for tea or ships for the sea, the common law has long implied a duty in contracts to provide things which are fit for the intended purpose. In time charters there is implied a duty tending to ensure that the ship is seaworthy.

The duty of seaworthiness is imposed at the beginning of the charter period and, like that in contracts for carriage of goods by sea, is both relative and absolute. It is relative in that the required level of seaworthiness is fixed by reference to the contemplated area of the world, the contemplated cargo, perhaps the state of scientific knowledge at the time, and, where relevant, the time of year. Fitness for June off Java may not be enough for January off Iceland. The relative nature of the duty is recognised in most countries. But in the common law world the duty is also absolute: once the level has been fixed, there is an absolute duty to achieve it. It is not so in The Hague Rules (art. III, r. 1): the carrier need only exercise due diligence to that end. It is not so in charters under the French droit commun: since 1898 the courts have recognised an exception ex lege of latent defects in the ship. However, this difference is less than appears for the common law has usually tolerated unambiguous exceptions of latent defect ex contractu.

The duty in time charters differs from that in voyage charters only in the impact of the contemplated time period on the relative level of the duty; short term repairs, enough for a voyage or two, may not be enough if the charter contemplates many months and many voyages.

Often the parties express the duty in the time charter. In most respects the express duty is like the implied duty. However, the express duty impinges either when the ship sails to the delivery port (New York Mail v. Eriksen (1922) 10 Ll.L.Rep. 666) or, being a contemporaneous affirmation, at the time of the contract (Scott v. Foley (1899) 5 Com. Cas. 53). In American law the express duty displaces the implied (Texaco v. Universal Marine 400 F. Supp. 311 (D.C. La. 1975); cf. Stanton v. Richardson (1874) L.R. 9 C.P. 390, 391). Further, the express duty may specify the technical characteristics required of the ship: see the Mobil Tanker Time Charter Party.

The longer the period of hire, the harder it must be to provide at the beginning a ship which, accidents apart, will still be seaworthy at the end. Should the owner be obliged to maintain the ship during the period? In voyage charters the question does not arise: the owner undertakes to deliver the goods safely at destination and failure, whether from unseaworthiness or any other unexcepted cause, makes him liable. But in time charters the basic duty is to provide a ship for a period and unseaworthiness arising during that period does not of itself make the owner liable in English law. Should it be otherwise?