Abstract: An interface module of a skimmer for a swimming pool or spa includes an adjustable face assembly that rotatably adjusts within an angular range, inward and/or outward with respect to vertical, that includes the expected possible angles of the pool wall, to provide a substantially planar mounting surface that is parallel to the wall of the swimming pool or spa. A waterproof shroud interconnects mounting brackets of the assembly, expanding and contracting as the mounting brackets are rotated relative to each other. The assembly can be integrated with the skimmer during manufacture of the skimmer, or poolside during skimmer installation. The installer positions the assembly approximate a skimmer aperture in the pool wall, actuates the adjustment mechanism of the interface module to select and lock the desired angle, and secures the interface module flush against the angled pool wall, with the throat module and vessel of the skimmer remaining upright.