Just like real fish, many different PHISH can be made with a "torque reaction engine", to provide different services.
This Phish will be capable of deployments measured in weeks to months:
Maneuverability: Rapidly steer in a tight turning radius using only the Torque Reaction Engine. Steering fins, like in real fish, will further enhance precise steering capabilities.
100' towcraft PHISH will efficiently haul barges, reduce diesel consumption, and produce radically less noise in the water.
A Torque Reaction Engine with no driveshaft will improve maneuverability of conventional PHISH and enable flagellum capable of swimming in pipes, mud, and other extreme environments.
Biomimetic PHISH can be made to look like, swim and interact with, and video eels, salmon, sharks, whales, and jellyfish.
Massive PHISH will generate power in rivers with reduced fish mortality.