From Longman Dictionary of Contemporary Englishdeep-seaˈdeep-sea adjective [only before noun] deep-sea fishing or diving is done in the deep part of the sea, far away from land
Examples from the Corpus
deep-sea• Further request immediate dispatch by plane to Thera Island two deep-sea divers with diving equipment for four, repeat four.• The Alvin is the lunar module of deep-sea exploration.• Local Activities: Walks, sailing, wind-surfing, deep-sea fishing, golf, sandy beaches.• The structures provide a measure of vertical relief sought by deep-sea invertebrates that make their living off particles in the water column.• Versions of his marine thermometer served for deep-sea measurements throughout the nineteenth century.• Austin agreed and I began work on my first, very modest contribution to deep-sea research.• There are few universities where one can specialize in deep-sea research.• Shell's large deep-sea tankers have been named after shells in an unbroken line since the launching of the Murex in 1892. 