See Slide Out Galley
It sounds like this boat doesn't have the slide out galley any longer. This boat came with a slide out galley that featured a stove, sink, and an ice chest. It would hide under the starboard cockpit settee area. The sink would line up over the drain hole you are asking about. I have seen the slide out galleys for sale. I don't know their official name.See either the attached photo, if this feature works, or the photo in the Catalina 22 owners photos. It is named, "Slide Out Galley".