Water-assisted liposuction, called Body-Jet, is a technique I've used for close to 3 years. It involves pulsing the local anesthesia solution under a slight pressure into the fat space, rather than the usual way of placing the fluid. Body-Jet is more like a power wash compared with a soaker hose method of placing fluid. It allows the anesthetic solution to placed more rapidly, and most importantly, in my experience more comfortably. The speed of pulses is adjustable.
The second tremendous advantage to Body-Jet is the ability to suction fat and simultaneously continue to place more anesthesia directly to the area being suctioned. This eliminates the occasional sensitive areas that may be encountered while suctioning. Even with the best technique placing local anesthesia, it is often necessary to stop suctioning to touch-up the anesthesia if there is a "hot spot". The Body-Jet method takes care of that without having to stop the suctioning.
A third benefit is that the gentle washing of the fat during suctioning makes it easier to extract the fat from the connective tissue to which it's anchored. This means less trauma to the tissue and there is less bruising in my experience.
A fourth advantage is that I've found I use less total local anesthesia with the Body-Jet method. This means a greater degree of safety by staying well within the accepted limits of local anesthesia.
The most important factor to a safe and succesful procedure is to see a surgeon who has a lot of experience with awake local anesthesia liposuction and an excellent safety record.