I suggest that when the globe coverage is under 100%, the big ocean filling the rest of the globe has its name showed several times (maybe three) to see it even if you are in another side of the globe where it is visible.
Another possiblity would be the name appearing when the previous visible name disappears.
I think this could be fixed for all areas of the map, in general. When I'm zooming around the map, and some zone (ocean, forest, swamp, whatever) is only partially visible on my screen, its name should be moved to the part of the zone that's currently visible.
It would be the best, but it looks complicated when you need to take account both movement and zoom.