This is not an oceanography website. But anyone who says that geography and oceanography are unrelated is insane, because where the land ends, the sea begins, and vice versa.
There is, though, a more worthwhile question here: is the Mediterranean Sea part of the Atlantic Ocean? Or should it be regarded as a separate body of water? Answer: It looks fairly independent when you view a map of the region, so there’s good argument for calling it a separate sea. Yet, it’s still clearly connected to the Atlantic Ocean. Just go to Gibraltar or Morocco and you can see for yourself.
However, what about the Bay of Bengal? Isn’t it really just a place where the sea happens to curve in? An even better example is Monterrey Bay off the coast of California. It’s hardly a bay, just a place where the ocean curves in a little (although down below the surface, there’s a lot more going on than you might think). That doesn’t seem like it’s separate from the ocean, really.
Getting back to the point: where do we define the end of the ocean and the beginning of the sea? Here is a good example of a map that just assumes every body of water that’s connected to an ocean is part of an ocean. There’s a lot of sense in that view, because it leaves very little doubt about the issue and makes the whole concept of “ocean” logical. But let’s remember that oceans themselves are all connected: the “Southern Ocean”, especially, is more a idea or concept than an actual body of water. Really, the oceans are one huge basin where most of the world’s rainwater drains.
Since oceans are considered to be separate but are connected, couldn’t you say that the seas are connected to the oceans but are separate bodies of water because they are partially separated from the oceans by land? Is some sort of middle ground in this debate necessary?
A middle ground is not necessary in this case, but helpful. If you look at a map, either regional or of the world, you can see that the Red Sea is almost a lake of its own; therefore, considering it to be separate from the Indian Ocean makes a lot of sense. Meanwhile, the Bay of Bengal, for example, should probably be considered part of the Indian Ocean because it is comparatively “open”. Still, there are some bodies of water that aren’t so clear: are the Gulf of Mexico and the Caribbean Sea part of the Atlantic Ocean? I (the Manager) lean towards yes, but the question should be left open for opinion. There is nothing wrong with opinion. Geography, especially in the naming of things, should have plenty of parts left open to opinion, because debate and discussion encourages recognition of geography as not an easy school subject, but instead a science based on logic and spacial understanding.