deep scattering layer (a layer in mid-depths of the sea detected by echo sounders, which rises at night and sinks during the day. Composed of organisms, many of which have a gas filled chamber, such as certain jellyfish and fishes)
False bottom.
См. Ложное дно.
(Источник: «Металлы и сплавы. Справочник.» Под редакцией Ю.П. Солнцева; НПО "Профессионал", НПО "Мир и семья"; Санкт-Петербург, 2003 г.)