The behavior of lubricants under sub-nanometer confinement remains poorly understood, limiting insight into fundamental lubrication processes. In this work, we employ molecular dynamics simulations to investigate the lubrication behavior of two-dimensional (2D) and three-dimensional (3D) water under such extreme confinement using a simplified model. We show that 3D water can reduce the coefficient of friction (COF) to below 0.01. In this regime, the wall shear stress is linearly related to the diffusion coefficient perpendicular to the shear direction but independent of the lattice structure. The lubricating effect of water is dominated by pressure. When water is compressed into a 2D state, it exhibits distinct stick‑slip‑like characteristics, leading to an increased COF above 0.02, which is influenced by both pressure and solid lattice structure. This study provides molecular-level insights into confined water lubrication, advancing the understanding of friction under nanoconfinement conditions.