Yes, that's the new Remora Class subs. It truly utilizes the primary benefit of the Cyclone "All Fuel" engine, specifically, it runs on any fuel.
The marine ecosystem on the bottom of Navy ships is one of the most bountiful on Earth. Keeping the Navy's bottoms clean is a big job, one might say.
The Remoras maneuver under a surface ship, parallel its path then rise to within a few inches of the ship's hull. A robotic arm sweeps a scraping device, called the Traction Planer/marine or "TP" for short, with each wipe removing organic material and biosolids from the bottom. This becomes the fuel for the Cyclone machinery.
Harry is so proud he's about to change his motto from "One Planet One Engine" to "Cyclone: Wiping Navy Bottoms with TP since 2015"
