As the banner says, if you qualify, you can log it. All OCNA Challenge caches are locationless type, arranged as Geo-Art in The Gulf of Mexico.They are all "unknown" (?) caches, owned by a special Admin account, OCNAChallenges. Do you have an idea for one? Feel free to contact us.
Lonely Cache (Level 3.5): Even in the most active areas there are caches that are lonely, having not been found for extended periods of time. For level 3.5 find five OCNA caches that have not been found for at least three full years. The previous "found" log must be dated 3 years prior to your "found" logs. A First to Find log is acceptable provided that the hide date is at least 3 years prior to the first find log entered. Cross listed caches are also acceptable provided that they have not been logged as found on any other listing service during the same period of time.
Each Lonely Cache Challenge entry must be unique. A cache that qualifies for more than one level may only be entered in one level. Choose the best entry for each Challenge. The exception is that you may use the same cache for Level 3, Level 3.3, and Level 3.5, so that you only need 5 total caches to log all three.
Also, if you found a lonely cache with another cacher, you may both use it to log the qualifying challenge cache. That fact that you were together should be noted in at least one of the logs for the lonely cache.
Verification: Please post your qualifying finds with your log, preferably in the http://coord.eu/OUXXXX format, and also keep in mind you can link to cache pages using our cache log editor, although is not mandatory. To see if you qualify, you can just look through your list of finds in your profile, but keep in mind, we do have the equivalent of a Groundspeak "my finds pocket query", (instructions here) and that .gpx file is easily imported into GSAK, or any similar stats program. We recommend a "gpx gc" file, and we also recommend GeoGet as a free alternative to GSAK, should you not be a paid full version user of GSAK.