Dive Units (Fray Universe)

Full Immersion Physical Simulators, better known as Dive Units or Divers due to their use of fluid suspension, are a type of virtual reality simulation equipment.
They take the form of an adjustable body frame within a thick plastic saline filled shell, a bodysuit attached to the frame, a fairly powerful computer, an air helmet, and a filter to keep the tank clean. Procedures exist to flush the tank if the mask seal breaks, breathing is obstructed, or the user goes into cardiac arrest.
The frame can be rotated to manipulate balance and the sense of motion, but the body is intended to be locked in place--touch and muscle movement are entirely simulated, decreasing the cost, maintenance, and safety concerns, although more articulated frames are in development as next generation Units.
The actual control and tactile feedback is accomplished by the skintight bodysuit. Said bodysuit is actually an enormous number of microelectrodes, tuned and wrapped to the contours of the body, so that it can artificially stimulate the nerves. The suit is then attached to the frame, through which the computer cables and air hose are routed, and the frame has emergency release mechanisms placed where the jands can be comfortably reach them, but designed that activating them is difficult to do by accident.
While microelectrodes are sufficient to simulate muscle movement, there is no viable way to directly simulate vision artificially, so it simply uses advanced goggles, which employ some very clever tricks to produce a higher definition 3D image than the system actually computes.
During login, users are rendered unconscious, partially to reduce the risk of discomfort or seizures, but mostly to take advantage of the body’s natural tendency to dream about being in positions it isn’t actually in, and believe its eyes over its actual tactile senses. When the user wakes in the gameworld, their entire body is stimulated somehow, generally with water or fierce wind, and this is actually a way to fool the brain into believing the false sensations it is being fed. The hands are still free and capable of movement, however, and can be used to pull the eject switch if necessary.
A full set costs about 500$, not including saline or filters, and it required some very clever marketing to actually sell, due to the required space and one player limit. It was originally marketed, along with it’s accompanying physics system, as an advanced military training device, designed to let soldiers simulate action in conditions well away from training centers, and after that became unprofitable, they offered a significantly cheaper version to the civilian market as a combination luxury bed and MMORPG. This actually became a runaway success, mainly because they decided on an open sandbox style crafting system, and it was sufficient for testing real gun, vehicle, and house designs.
Now, they’re fairly common, at least partially because they really can be quite comfortable to sleep in, allowing them to take the place of the bed in many small apartments owned by geeks. A fairly popular, slightly more traditional MMO named Fray was released for it about five years ago, with the distinction of being a similar work in progress, most notably in the form of it’s debugging; Several professionals and many players take the role of the Red Team, trying to break the ingame society in any way possible...