Neptune, the Roman god of the SEA, is also known as the King of the SEA. His kingdom is the OCEAN, which is made up of many seas. The term 'Neptune, Kingdom of' can be broken down into two crossword solutions: OCEAN (5 letters) and SEA (3 letters). OCEAN refers to the large body of salt water that covers most of the Earth's surface, while SEA is a smaller body of salt water that is partially enclosed by land. Together, these two words represent Neptune's dominion over the vast expanse of the OCEAN and its many seas.