If you're looking to communicate the opposite of being "in-undated", consider words like "empty," "desolate," or "unpopulated." These words communicate a sense of being bare, vacant, or without the presence of something (whether that be people, messages, or water). "Clear" or "uncrowded" could also be considered antonyms for "in-undated," as they similarly convey a space that is not overwhelmed or overrun by a particular substance or force. Whatever word you decide to use, make sure it captures the intended meaning accurately in a way that supports clear communication.