Single-layer MoS₂ has been shown to excel in many applications like as a catalyst, supercapacitor, transistor, and biosensor. It has been shown that there is a correlation between the catalytic activity and the metallic character of the surface. Consequently, the metallic phase of MoS₂ has been shown to surpass the performance of the semiconducting phase. However, the metallic phase is less energetically favorable than the semiconducting 2H phase, and it is unstable in air. Recently, it has been shown that a metallic phase of MoS₂ is stable in water. This metallic phase is also found to be hydrophilic which provides additional advantages in applications as a supercapacitor or biosensor. We attribute this metallic phase to 1T′-MoS₂ and investigate the origin of the hydrophilic behavior. Through first-principles calculations, we found that, with a sulfur vacancy on the surface, dissociative adsorption of a water molecule is favorable only on the 1T′ surface. The water dissociation on the surface not only increases the hydrophilicity of the surface, but it also explains the enhanced stability of 1T′-MoS₂ in water by reducing the energy difference between the 1T′ and 2H phases.