Unexpectedly high efficiency stimulated Raman scattering are seen in micrometer-sized water jets. The pumping laser beam of a 100-W frequency-doubled Nd:YAG laser is coupled into the water jet similar to an optical fiber. The light is guided within the water jet, providing a high irradiance level throughout its stable portion (typically 60 to 80 mm in the case of a jet of 60 µm in diameter). This results in a long interaction length between the high intensity beam and water. At irradiance levels, one order of magnitude smaller than the breakdown threshold 26.7% of the pumping light was converted to Stokes emission. A single stimulated Raman scattering (SRS) peak at 653 nm (3489 cm–1 in wavelength shift) is observed to be emitted from the jet in the upstream direction, which is different from the spectra reported in the case of bulk water or small water cylinders.