Is it possible to add a prefix to the word ocean?
Also, is it possible to add a suffix to it as well?
The short answer is yes. It is the nature of productive affixes that they can be freely applied to any word of the appropriate category to derive new words.
The longer answer depends on several things. One is just what you mean by prefixes and suffixes. I’m going to assume that you do not mean merely to combine ocean with an existing, freestanding word to create a compound word such as occurs with ocean-sea, world-ocean, ice-ocean, ocean-deep.
Rather, I believe that you mean prefixes and suffixes that cannot stand on their own. If so, then there is no reason that you cannot, provided that the affix chosen is one that can apply to words like ocean. There are zillions of these combining forms, and so there are zillions of possibilities.
If your question is whether it is ever valid, or even just in this case, to apply both a prefix and a suffix to an existing word, then the answer is a resounding yes. Consider:
Just one example of a word derived from ocean using both a prefix and a suffix is interoceanic; many others are possible.
If you are thinking of a particular prefix or suffix, then I imagine that the reason you are asking this question is that you have looked up the resulting word in some dictionary or another, but failed to find the word you are looking for.
If so, then this might mean you are trying to use an affix in a way which that affix cannot reasonably be used in. For example, you won’t find *y-oceant in any dictionary, because those aren’t really affixes that lend themselves to ocean.
However, it might also mean that your word is not (yet?) common enough to be included in the dictionary you were checking for it in. That doesn’t matter as to whether you can do it or not. Putting units of language together in arbitrary combinations is central to what makes language, language. This is true of individual words (“free morphemes”) and for combining forms (“bound morphemes”) alike.
So for example, even though I could find these in no dictionary, one could well imagine words like mini-ocean, super-ocean, ur-ocean, or even über-ocean. Those are all words that might someday occur, and indeed, may well have already occurred — somewhere and somewhen.
This only works for what are called “productive” affixes, a word that means they can be used at will to create any which word the coiner desires.
However, many prefixes and suffixes are no longer productive in English, which means you don’t get to do this with them anymore even though people once did so. If you try to use an affix that is no longer productive, people might not know what you meant by it. But if it is, they should.
No dictionary in existence ever lists all possible derived words, not only because their meaning in the case of productive affixes should be clear to any native speaker who reads them, but more importantly because the combinatoric explosion of possibilities would make listing all possibilities impossible.
Here, though, are some of the words mentioned by the OED which were derived by adding a prefix, suffix, or both to the word ocean:
This is only a sampling; please feel free to create your own. Several of the words listed above the OED calls “nonce-words”, which means they were created on the fly for one particular use, but whose use never really caught fire and spread to other authors. Many words like this exist in English, and it is the nature of language that we can create what words we will as need arises.