  Superconducting single crystal samples of Na_xCoO_2 + yH_2O have been
produced using an electrochemical technique which dispenses with the usual
bromine chemical de-intercalation step and permits much more precise control of
the Na content. After careful hydration, nearly single-phase crystals have been
obtained in which over 90% of the sample's volume corresponds to the
superconducting Na_{0.3}CoO_2 + 1.3H_2O structure. Susceptibility and specific
heat measurements confirm that bulk superconductivity has been achieved. The
extracted normal state density of states indicates Fermi-liquid behavior with
strong mass enhancement and a modest Wilson ratio. Measurements of H_{c2} for
H||c and H||ab reveal significant anisotropy. The estimated value of H_{c2} for
H||c yields a coherence length of ~100 A, consistent with an extremely narrow
bandwidth.
