Local and global three-dimensionality of cavity interfaces near detachment was examined. Cavities forming on hydrophilic test objects at higher Reynolds numbers (Re>105) exhibited a local flow structure in the cavity interface called ‘divots’. Divots resulted from a local breakdown of the two-dimensional laminar boundary separation. Divots did not form on hydrophobic test objects. Instead, at higher Reynolds numbers (Re>105), the cavity at detachment was composed of a series of wedge shaped structures. Flows with strong adverse pressure gradients upstream of cavity detachment exhibited only local three-dimensionality near one cavity detachment. Flows with weak adverse pressure gradients upstream of cavity detachment were more susceptible to breakdown into global three-dimensionality. This was the case for cavitation on the hydrofoils. Holographic particle imaging velocimetry (HPIV) was used to examine the spanwise and streamwise variation of the flow upstream of the cavity detachment. Three-dimensionality of the cavity detachment was associated with strong variations of the flow upstream of the cavity in the direction perpendicular to the mean flow direction.