new approach to jet packs where water is used as a high-density propulsion fluid. This requires a very large mass of fluid that makes a self-contained jet pack infeasible. Instead, this approach separates the engine, fuel and fluid supply from the pilot's flying apparatus, using a long flexible hose to feed the water to the jet nozzle pack attached to the pilot's body. These inventions are known as "hydro jet packs", and successful designs have used jetski technology as the powerplant operating in a body of water (an ocean, lake, or pool) to provide the needed propulsion. Several hydro jet pack approaches have been successfully tested and put into production. Flow rate can be controlled by a throttle operator on the jetski, or by the pilot using a remote actuator. Another significant difference with hydro jet packs is that they can be operated below the surface as well as above it. As of 2013, many hydro jet pack rental businesses are operating in various locations around the world. JetLev The JetLev was the first hydroflight jet pack on the market, and its makers were awarded the first patents, in 2008, for hydro jet packs. The JetLev has the appearance of a typical jet pack, with two nozzles on a backpack propelling the rider upwards. It just has an umbilicus to the powering jetski that provides the water for the thrust used. Flyboard A Flyboard has water jets under each of the pilot's feet. An optional feature is a lower-thrust water jet for each arm for greater control. The powerplant is a regular jetski. Development for this approach was started in the spring of 2011. Firefighters Firefighters in some parts of the world use jet packs which help them to fight fires close to the sea or a water body. The jet packs use water and there is no need for a fire truck or water tank. Home-made versions Episode 32 of MythBusters investigates the urban legend of an affordable jet pack or rocket pack that can be built from plans purchased on the Internet. Extensive modifications were made by the MythBusters team due to vagueness in the plans and because of the infeasibility of the specified engine mounting system. The jet pack produced by MythBusters had two ducted fans powered by ultralight-type piston engines. (Fans complained that the use of piston engines destroyed the whole idea of the pack's being