This dataset contains raw spectral data associated with the main and supplementary figures of a publication detailing how surface water monolayers in sub-nm gaps between gold nanoparticle surfaces can be observed using surface-enhanced Raman spectroscopy (SERS). SERS data were collected at 5-10 positions on a multi-layer gold nanoparticle aggregate (MLagg) substrate in a range of conditions, and are normalised for laser power and integration time. All measurements are taken at room temperature unless otherwise specified and Raman shifts are calibrated with respect to Si. The SERS dataset characterises the MLagg substrate in air, water, and DMSO, demonstrates how the surface water changes with deuteration and subsequent drying in nitrogen flow, and the effects of an applied potential.