Sea is the opposite of Sky. you are likely to find Sky in/at/on Planet. you are likely to find Coast in/at/on Planet. 
Political is related to Treaty. Treaty is related to Peaceful. Peaceful is derived from Peace. Peace is related to Lot. 
Sea <--Antonym--> Sky --AtLocation--> Planet <--AtLocation-- Coast 
Political <--RelatedTo--> Treaty <--RelatedTo--> Peaceful --DerivedFrom--> Peace <--RelatedTo--> Lot 