Solitary internal wave packets were observed in May 1999, propagating toward the east coast of Korea with thermocline displacements up to twenty-six meters downward from the initial depth of twenty meters. High nonlinearity of these waves is represented by the second-order KdV model better than KdV equations. Regular occurrence of solitary internal wave packets with the period of about nineteen hours suggests the generation by near-inertial internal waves, which has not been reported in the literature yet. ¿ 2001 American Geophysical Union