The trajectories of several Argo floats are studied to investigate the mid-depth circulation in the southwest Pacific that coincides with the spreading of the Antarctic Intermediate Waters (AAIW). Before entering the Coral Sea, the floats converge and join the North Caledonian Jet (NCJ) south of 15°S. These observations suggest that the waters transported by this jet do not have a unique source. Hydrologic parameters and oxygen concentration confirm that the characteristics of the AAIW in the NCJ result from a convergence and a mixing of waters from the northern limb of the subtropical gyre and from the southeastern New Caledonian region. The northern contribution is associated with the water masses transported by the North Vanuatu jet that re-circulate in the region between the D'Entrecasteaux reefs and the Vanuatu archipelago. It is shown that such complex dynamical features could be reproduced by numerical models when their horizontal resolution is sufficiently high.