Literally, The word ocean comes from the Greek word okeanos (great stream encircling the earth's disc) And then converted into Latin --> Old French --> English.

Ocean is a main element of the creation history of living creatures on earth which keeps a large area covered by salted water between continets.

In Greek Mythology, There was a concept of A single massive body of water surrounding the earth, The Greek called Okeanos. And then this word turned into English word 'Ocean'.

The creation of oceans was a long process. There was a Magma Ocean at first (probably). Magma is the molten natural element of a planet That creates all of the volcanic rocks. This process probably happened 4.54 billion years ago. As the Earth gradually cooled, these volcanic lavas evaporated and gathered in the sky to form clouds. Then it rains, but the earth is not cooled enough to evaporate again, forming clouds. In this process, when the Earth reaches stable cold temperatures, these waters become permanent. Oceans finally started forming 3.8 billion years ago.

No, I don't think so. As you know, every creation have a creator (directly or indirectly). Scientifically, we got as it as a nature's behavior. But, is it same to what actually happened?
I don't know everything. But, I think there is a power beyond science and human exploration. It exist but we can not actually observe it. It might be be different then what we can feel/ see/ explore. Example:

1. Our eyes which can see
2. Hollywod movies
Yes, we missed something else, which is exist but we can not see.
3. Hollywood movie's shooting

1. Our eyes ----> Our exploration power
2. hollywood movies ----> Science
3. hollywood movie's shooting ----> Something else (legendary)