Is it possible to get Reverse Geocode to detect oceans?

I'm not familar with the nominatim way of doing reverse-geocoding but guess that oceans (or anything outside the coastlines) is filtered during import. Can anybody plz. confirm?

Maybe you can try some other engines listed in the OSM wiki at Search Engines

You cannot detect ocean (area) objects in OSM by any geo-search model. Simply, der is no such class of objects (and OSM is not an exception). But, it is possible to create these oceans indirectly, though it is a complex and complicated task. So, if you are research and programming enthusiast, try the following option (major steps in bullets form):
1.Extract from an OSM dump the coastline data as poly-lines. Optionally, change the projection. Roughly, over 750 thousand poly-lines with over 32 million nodes.
2.Remove the redundancy (replications, overlaping sections...).
3.Connect the poly-lines (linear connections) into polygons. If needed perform gap reparations.
4.Transform the polygon set into (simple) area objects/structures. You can expect some 500 thousand area objects containing totally some 1000 holes. These are the land masses of the Planet.
5.Invert the land areas into water areas (e.g. add the global/Planet polygon and repeat the restructuring). You will get just some hundreds of planet_sea areas, though, some really very large.
6.Extract from the former sea areas the largest one and you get the Planet's global ocean. Roughly, this is everything outside the continents and islands. The global ocean contains more than 480 thousand holes and be careful with rendering especially without prior tiling.
Now, you can divide the global ocean into the traditional ocean areas.