The word for ocean in Spanish is océano. It is a masculine noun, so you would use el before it, making it el océano.
For example, if you want to say “The ocean is beautiful,” you would say El océano es hermoso.
Spanish, like English, has different words for bodies of water. While océano refers to the vast bodies of saltwater that cover most of the Earth’s surface, smaller bodies of water like seas, lakes, and rivers have their own specific terms.