According to English law, in a voyage policy there is an implied warranty that at the commencement of the voyage the ship shall be seaworthy for the purpose of the particular adventure to be insured. However, Unites States law affords the implied warranty of seaworthiness a great deal of latitude. In the case of voyage policies, it has been traditionally held that the assured is bound not only to have his vessel seaworthy at the commencement of the voyage but also to keep her so, insofar as this can be achieved by himself and his agents, throughout the voyage. Additionally, a defect in seaworthiness, arising after the commencement of the risk, and permitted to continue from bad faith or want of ordinary prudence or diligence on the part of the insured or his agents, discharges the insurer from liability for any loss consequent to such bad faith, or want of prudence or diligence; but does not affect the insurance contract in reference to any other risk or loss covered by the policy, and which is not caused or exacerbated by the aforementioned defect. One of the most important areas of difference in the marine insurance contract between the U.K. and U.S. is the breach of warranty. Prior to the Wilburn Boat case, the MIA was thought to hold that the effect of a breach of warranty was similar under American law -in that under the general maritime law literal compliance with all promissory warranties is required. In this case, the Court concluded that state law should apply to a marine insurance policy, and found that there was no federal rule addressing the consequences of a breach of warranty in marine polices. However, it is of the utmost importance that this case brought to a close the imperative concordance between English and American law. Meanwhile, in relation to marine insurance contracts in Korea, this insurance is subject to English law and practice;, additionally, the international trade volume between Korea and the United States has assumed a vast scale. Therefore, we believe it is important to understand the differences in marine insurance law between the two countries in terms of marine insurance contracts, and most specifically warranties.