The ship must follow the voyage which is mentioned in the policy. If the course is not specified, it must follow the usual and customary course. If the ship sails from a different destination other than mentioned in the policy then the risk does not attach.
If a ship sails by an unusual course, from the one, mentioned in the policy, then it takes place a deviation of the voyage. Where a ship deviates from the voyage mentioned in the policy, the insurer is discharged from liability. But the insurer is liable for any loss which occurred prior to the deviation.
When deviation of voyage is excused :
1. Where it is authorised by any special term in the policy;
2. Where it is caused by circumstances beyond the control of the weather
3. Where it is reasonably necessary in order to comply with an express or implied warranty ;
4.Where it is reasonably necessary for the safety of the ship or the subject matter insured;
5. Where it is necessary for the purpose of saving human life where human life is danger;
The ship must resume her course with reasonable dispatch, as soon as the causes which excuse deviation or delay cease to operate.
Also read about marine insurance
Deviation of voyage Deviation of voyage Deviation of voyage Deviation of voyage