We present the structure and magnetic properties of the honeycomb anhydrate NaNi2BiO6-delta and its monolayer hydrate NaNi2BiO6-delta center dot 1.7H(2)O, synthesized by deintercalation of the layered alpha-NaFeO2-type honeycomb compound Na3Ni2BiO6. The anhydrate adopts ABAB-type oxygen packing and a one-layer hexagonal unit cell, whereas the hydrate adopts an oxygen packing sequence based on a three-layer rhombohedral subcell. The metal-oxide layer separations are 5.7 angstrom in the anhydrate and 7.1 angstrom in the hydrate, making the hydrate a quasi 2-D honeycomb system. The compounds were characterized through single crystal diffraction, powder X-ray diffraction, thermogravimetric analysis, and elemental analysis. Temperature-dependent magnetic susceptibility measurements show both to have negative Weiss temperatures (-18.5 and -14.6 K, respectively) and similar magnetic moments (2.21 and 2.26 mu(B)/Ni, respectively), though the field-dependent magnetization and heat capacity data suggest subtle differences in their magnetic behavior. The magnetic moments per Ni are relatively high, which we suggest is due to the presence of a mixture of Ni2+ and Ni3+ caused by oxygen vacancies.