In October and early November 1999, the GOGP99 experiment collected hydrological, currentmeter, tide recorder, thermistor and drifting buoy data near the Strait of Hormuz. Data analysis provides the water mass structure in the Strait: Persian Gulf Water (PGW) core is banked against the Omani coast, while Indian Ocean Surface Water (IOSW) lies near the Iranian coast. These water masses are most often covered by a homogeneous surface layer. Thermohaline characteristics of the PGW core decrease substantially downstream, from the Persian/Arabian Gulf to the Gulf of Oman. PGW and IOSW thermohaline characteristics and distribution also exhibit notable changes at periods shorter than a month as shown by repeated hydrological sections. The tidal signal measured south of the Strait by moored ADCP and thermistor chains has predominant semi-diurnal M2 and S2 and diurnal K1 components and possesses a complex vertical structure. Tidal intensification near the surface pycnocline is associated with noticeable internal waves. At subtidal timescale, mooring recordings confirm the water mass variability observed in the repeated hydrological sections. The mixed layer also deepens substantially during the 1-month period. Finally, trajectories of surface buoys drogued at 15 m exhibit reversals over periods characteristic of changes in wind direction.