Are liquids compressible ?
Compressibility of any substance depends inversely on the “Bulk Modulus” of the substance. Bulk Modulus is a simple ratio of the stress (change in pressure) applied on a body and the relative change in volume caused by the stress. So to have 0 compression you need to find a substance that doesn’t respond by changing its volume even to infinite pressure (or 0 change in volume to any range of pressures). The above case is hypothetical as even solids are effected (by the change in volume) minutely by large pressures.