Water, as a component of body fluids, acts as a lubricant and shock absorber. Water is good for storing heat and protects the body from extreme temperature variations. Liquids such as water compress very little, if at all. This makes them generally a poor choice as a shock absorber.
If you suspend a pilot in a sphere of water and hit the water with a stick, the impact will spread to the pilot relatively easily. If, on the other hand, the impacting object rotates, a much smaller part of the impact energy is absorbed, and most of it is used to keep rotating the object. Suspending the pilot in a fluid allows the fluid to transmit the force of the impact to the shock absorbers, regardless of the direction from which the impact occurs (basically, we would be the piston of a giant hydraulic shock absorber). For example, adding water transforms cornstarch into a material commonly known as Oobleck, while adding oil transforms cornstarch into an electro-rheological fluid.
Instead, when an impact force is applied to the liquid, some of the liquid flows into an alternative container, where a more traditional shock absorber is located. Sudden spikes in water pressure can damage pipe fittings, so the damper provides a low-resistance path for water to reach where additional kinetic energy is absorbed by a spring, pneumatic piston, or gravity.