An insurance contract is one under which, for some considerations, the policyholder secures to himself some benefit upon the occurrence of an uncertain event beyond his own control and adverse to his interests by transferring some or all of the risk to the insurers. Thus according to the general principle of insurance: insurance is a commodity to protect against casualties and against unforeseeable losses. An issue arises where an unfit vessel is unable to encounter ordinary perils while at sea, and where such unfitness could have been avoided had the shipowner excised due diligence to make the vessel properly equipped, manned and maintained; the risk caused by the unfitness would be foreseeable and outside the scope of insurance in principle. Thus in marine insurance contracts, there are corresponding rules to prevent such certain risks. The practical significance for such rules is that the insurer can value the risk properly and adjust the premium accordingly without facing certain risks caused by substandard ships. Examinations on such rules under English and Norwegian jurisdiction will be presented in this paper. The United Kingdom is well known as the international market center of marine insurance ; while on the other hand an extensive and far-reaching internationalization of the Norwegian Marine Insurance Market has been observed since the early 1980s. A comparative look between the dominating English marine insurance market and the competitive Norwegian marine insurance market should in my opinion therefore be interesting.