Another issue important in the marine insurance area is misrepresentation or concealment. The marine insurance contract is one which requires the highest degree of good faith. Any misrepresentation of a fact which is material to the underwriter will void the policy. In addition, a policy can be void for breach of any of the warranties implied by law or expressed in the policy. The most common is the implied warranty of seaworthiness of the insured vessel or of the vessel carrying insured goods.
Seaworthiness is a general term but is has been narrowed by case law.
A ship which is seaworthy for a southern voyage may not be so for a transatlantic crossing in winter. Similarly, in cargo policies, the warranty of seaworthiness of the vessel includes fitness to carry a particular cargo. In voyage policies, the doctrine of deviation states that the underwriter is deemed to have intended to accept only that risk that inheres in the expeditious prosecution of the voyage by the usual commercial route. If, without justification, the vessel departs from the route, or delays unreasonably in pursuing the voyage, the policy will be voided. Once voided by a deviation, the insurance contract is canceled for good and not restored by a return to the proper course.