Marine is related to Fish. Fish is related to Being. Being is related to Believe. Believe is a synonym of Buy. 
Rural is related to Urban. Urban is related to Place. Place is related to Cross. 
Marine <--RelatedTo--> Fish <--RelatedTo--> Being <--RelatedTo--> Believe <--Synonym--> Buy 
Rural <--RelatedTo--> Urban <--RelatedTo--> Place <--RelatedTo--> Cross 