FYI, Oceania's world cruises are on Insignia, not Nautica.
If someone is on the full Oceania ATW a full visa package is included, so it's unlikely the OP is on that cruise as they would likely know that all necessary visas can be obtained through the visa service contracted by Oceania. Even if they are only on a segment they can pay Oceania's visa service provider to get the proper visa.