The experience of a lifetime in the gulf of tonkin grab your chance to explore halong bay natural wonder a unesco world heritage site of cultural and historical significance on a unique 3 days 2 nights cruise with the au co with a wide range of activities on board and extra the au co promises you a most memorable experience while discovering the gulf of tonkin and enjoying your time whether you choose to explore hidden caves by kayak or bamboo boats swimming in the emerald waters cycli