The Indonesian Throughflow (ITF) is the leakage of western tropical Pacific water into the southeastern tropical Indian Ocean through the Indonesian seas. The ITF is an important pathway for the transfer of climate signals and their anomalies around the world oceans. While the heat and fresh water carried by the ITF are known to affect the basin budgets of both the Pacific and Indian Oceans, the magnitude and vertical distribution of the ITF are not well known, giving little guidance to the initialization and validation of ocean circulation and climate models. In response to this lack of knowledge, the International Nusantara Stratification and Transport (INSTANT) program was established to directly measure the ITF. Scientists from Indonesia, France, the Netherlands, United States, and Australia make up the collaborative INSTANT partnership.