sea coal (noun)

1. Why was the coal at the beach so popular? Because it was a real sea coal!

2. The fireplace in the living room is made of sea coal, giving it a distinct and modern look.

3. In the movie, the protagonist is imprisoned in a dark underground chamber fueled by sea coal.

4. In the futuristic world of the novel, they harness the energy of sea coal for interstellar travel.