A vertically sheared eastward jet in the equatorial Pacific in late 1991 and early 1992 carried relatively fresh water from the western Pacific overriding the saltier surface layer of the central region. Salinity anomalies of about −1.0 psu were observed over a period of several months in a surface layer 50 m thick near the equator. Below this fresh layer them was a steep halocline having very little temperature stratification, so that the density changes were dominated by salinity. In December 1991, eastward surface velocities in the fresh jet at 170°W were 100 cm s−1 with a shear of about 40 cm s−1 in the top 100 m; the core of the jet was about 200 km in width, centered at 1.5°S. The jet decayed and vanished over the next few months, though the surface halocline remained. A simple extension of the familiar 1½-layer model can account for the initial development of the sheared eastward jet. The surface pressure gradient in this initial value problem, tending to accelerate the fluid eastward, diminishes with depth because there is a zonal salinity gradient in the initially mixed layer. The depth dependence of the pressure gradient causes the accelerating flow to be vertically sheared, resulting in a tilting over of the isohalines. The shear progressively unmixes the mixed layer. The vertically integrated part of this solution is the Yoshida jet. The depth-dependent part of the solution results from a local conversion of potential to kinetic energy as the tilting isohalines lower the center of gravity of the surface layer. For added realism, generalizations of the model include wind forcing and a meridional salinity gradient. While not discounting the conventional explanation of westerly wind stress in driving the eastward jet, it is shown that the tilting/shearing mechanism can be comparable to wind stress and is important in the production of salinity barrier layers. Fresh equatorial jets may provide a key to a better understanding of the physics of tropical ocean circulation and air-sea interaction during El Niño.