The term 'Blue Sea' can be broken down into two crossword solutions: DEEP (4 letters). The term 'DEEP' is an adjective that describes something that is far below the surface or far away from the shore. It is often used to describe the ocean, which is why it is a fitting solution for the term 'Blue Sea'. The term 'Blue Sea' is often used to describe the DEEP blue color of the ocean, which is why the solution 'DEEP' is appropriate.