According to Official Guinness Records,
The record for the fastest time in which any known marine animal has been tracked completing a return migration across an entire ocean, is nine months and belongs to a great white shark that swam approximately 20,000 km (12,400 miles). On 7 November 2003, a team of researchers led by Dr Ramón Bonfil from the Wildlife Conservation Society (USA) electronically-tagged four sharks in South Africa, one of whom was nick-named Nicole (after the Australian actress and shark-lover, Nicole Kidman). In August 2004, Nicole was identified off the coast of South Africa, yet her timed-release tag was recovered in Australia six months earlier in February, where a satellite recorded its transmission. Thus, within nine months, Nicole had swam from South Africa to Australia and back, and in doing so completed the first – and the longest – recorded journey of a shark, crossing an entire ocean back and forth.
During her trip, she also reached the greatest depth reliably measured for a white shark, 982 m (3,221 ft).
For a complete list of 2004 records, please visit 2004 Guinness Records in South Africa.