For a long time, marine biologists have used "slurp guns" of various types to suck in marine creatures and bring them back for examination. Keeping a deep-sea critter alive, though, is a tricky process. Changes in pressure are often fatal.
French scientists have created a solution, the Projet d’Enceinte de Remontée Isobare Servant la Capture d’Organismes Profonds ("Enclosure project for isobaric ascent serving to capture deep organisms"). PERISCOP is a suction device with three chambers: one to capture an organism, one to maintain it while the submersible or ROV continues to cruise at depth, and one to maintain water pressure while you bring the organism to the surface and transfer it into a shipboard pressure tank. It's a little more complex than most such devices but it increases the depth from which pressure-sensitive fish and other animals can be safely retrieved (or kidnapped, I suppose, from the fish's point of view.) The prize so far is an eelpout brought up alive and healthy from 2,300m.