The title compound is orthorhombic witha = 26·132(6),b = 11·023(2),c = 8·317(5), Å; space group Iba2;Z = 8,Dm = 1·21(1),Dc = 1·192 Mg m−3, 1/2(H2O) per molecule in asymmetric unit; λ (MoKα) = 0·7107A; μ = 0·46 cm−1; F(000) = 936. The structure was solved by direct methods and refined to R(F) value of 0·069 using 327 reflections withF ≥ 5σ(F) out of 727 independent reflections for2τ max = 46°. Thetrans fused cyclohexane and cyclohexanone rings form layers along thea-b plane. The axial methyl attached at the bridge-head, interlocks with the translated methylene of the cyclobutane fused across the cyclohexane ring. The equatorial hydroxyl at the bridge-head adjacent to the methyl junction and the water molecule on the two-fold form a water bridge along thez axis. The packing is reminiscent of that observed for the cholesterols used in membrane structure studies.