Cooling apparatuses, cooled electronic modules and methods of fabrication are provided for fluid immersion-cooling of an electronic component(s). The method includes, for instance: securing a housing about an electronic component to be cooled, the housing at least partially surrounding and forming a compartment about the electronic component to be cooled; disposing a fluid within the compartment, wherein the electronic component to be cooled is at least partially immersed within the fluid, and wherein the fluid comprises water; and providing a deionizing structure within the compartment, the deionizing structure comprising deionizing material, the deionizing material ensuring deionization of the fluid within the compartment, wherein the deionizing structure is configured to accommodate boiling of the fluid within the compartment.