Better known as virt-sims. They are full-immersion virtual reality machines that use smart fluids, capable of moving and changing densities and temperatures to a very high granularity. The user immerses themselves in a large tank, providing full freedom of movement, audio, video and olfactory stimulation are provided through facemasks which also feed oxygen to the user. For the majority of users, they are capable of perfectly simulating reality, and they are widely used in both athletics and military training, allowing for dangerous simulations that would be otherwise untenable.