Refer Sec 172 of IT Act. If the shipping company is a non-resident, then TDS is not applicable on ocean freight subject to a exemption certificate received from the company issued by the IT department.
Though 7.5% of ocean freight is chargeable u/s 172 of the IT Act,it is not chargeable under the provisions of 195,194C of theIT Act,as per circular No 724 of 1995.
TDS will be applicable to ocean freight u/s 194 C only in case of resident not acting in the capacity of agent of Non resident shipping cos. i.e. outside purview of section 172.