A charter agreement, what I understand, is an agreement for hiring a vessel or a part of the vessel for conveyance of goods or passangers. It is the contract between the owner of a vessel and the charterer for the use of a vessel. No matter what the size is, but Ships are tangible goods. Where there is a Charter Party agreement, the charterer has exclusive right to use a vessel or specific place on it. Hence it amounts to supply of tangible goods for use.
It's not always true that when ship is being used for transportation of goods no service tax should be levied. To my knowledge in case of transport of coastal goods, service tax is levied.
Please mention the provisions, if any, for non levy of service tax on transportation through ship.