Wave-flume laboratory experiments were conducted to study the mechanism of fluidization of partially consolidated mud beds, under wave propagation. The mixture of commercial kaolinite and tap water was allowed to partially consolidate under its self-weight before initiating the progressive wave propagation. The vertical changes in pore water pressure in the mud bed were monitored by using sensitive pore pressure transducers, at three levels across the mud layer depth. The experiments revealed that the wave characteristics and bed properties strongly affect the complex fluidization process, in which the accumulated pore water pressure develops through four transitional stages. The accumulated pore water pressure increases sharply at the first stage, which is followed by further gradual increases in the next two stages, with different rates. The breakup of aggregated mud particles, i.e. the generation of fluid mud, is observed at the last stage, resulting in a partial dissipation of accumulated pore pressure and wave height attenuation. The measurements also revealed that the fluidization starts from the top of the mud layer, and proceeds to the underlying layers.