Structure and dynamics of water confined in channels of diameter of few nanometer in size strongly differ from the ones of water in the bulk phase. Here, we present radiowave dielectric relaxation measurements on water-filled single-walled carbon nanotubes, with the aim of highlighting some aspects on the molecular electric dipole organization of water responding to high spatial confinement in a hydrophobic environment. The observed dielectric spectra, resulting into two contiguous relaxation processes, allow us to separate the confined water in the interior of the nanotubes from external water, providing support for the existence in the confinement region of water domains held together by hydrogen bonds. Our results, based on the deconvolution of the dielectric spectra due to the presence of a bulk and a confined water phase, furnish a significantly higher Kirkwood correlation factor, larger than the one of water in bulk phase, indicating a strong correlation between water molecules inside nanotubes, not seen in bulk water. © 2012 American Institute of Physics.