  Poly- and single-crystalline Na$_x$CoO$_2$ has been successfully intercalated
with H$_2$O and D$_2$O as confirmed by X-ray diffraction and thermogravimetric
analysis. Resistivity, magnetic susceptibility, and specific heat measurements
show bulk superconductivity with T$_c$ close to 5 K in both cases. The
substitution of deuterium for hydrogen has an effect on T$_c$ of less than 0.2
K. Investigation of the resistivity anisotropy of Na$_x$CoO$_2\cdot$yH$_2$O
single crystals shows: (a) almost zero resistivity below T$_c$, and (b) an
abrupt upturn at $T^* \sim$ 52 K in both the $\it {ab}$ plane and the $\it {c}$
direction. The implications of our results on the possible superconducting
mechanism will be discussed.
