Indian and French naval ships took to the seas off Goa as part of the sea phase of Varuna, the largest Indo-French naval exercise till date, a statement issued by the Indian Navy on Wednesday said.French nuclear powered aircraft carrier Charles de Gaulle and French Navy ships Provence, La Touche Treville, Forbin and tanker Marne along with a submarine will conduct inter-operability exercises along with Indian naval ships INS Chennai, INS Mumbai, INS Tarkash, tanker INS Deepak and a submarine."The two navies will conduct extensive evolutions to further inter-operability and professional skills towards better maritime cooperation," the statement said.The bilateral naval exercise initiated in 1983 and christened 'Varuna' in 2001 forms a vital part of the Indo-French strategic partnership and has grown in scope and complexity over the years.The harbour phase of the exercise concluded on May 6 while the sea phase, which has already witnessed air-to-air combat, air defence exercises, anti-submarine exercises and surface shoots, will end on May 10.