Well ok, anyway, it's not a bug. Your culture can't spread out into the open ocean. As cool as that would be, it can't happen.
You'll see if you play a continents map, that in the modern era (for example), when everyone has fully claimed all space on their continent, that the mini-map shows all coloured areas will not meet. They'll just surround the continent, but not spread across to the next.
You'll see if you play a continents map, that in the modern era (for example), when everyone has fully claimed all space on their continent, that the mini-map shows all coloured areas will not meet. They'll just surround the continent, but not spread across to the next.