The International Conference on Hydrodynamics (ICHD) conference series was initiated in China in 1994 and has been held biennially ever since in Asia. It has become an important event at which academics, researchers and practitioners exchange new ideas and their research findings. The proceedings of the 2004ICHD conference, held in Perth, contains a selection of invited keynote lectures and refereed papers. The papers cover a wide range of topics such as naval architectural and ocean engineering, coastal and offshore engineering, industrial fluid mechanics, heat and mass transfer, environmental fluid mechanics and hydraulics, water resources, fundamental fluid hydrodynamics and computational fluid mechanics.