Plane-wave reflection and transmission coefficients were calculated for a porous viscoelastic seabed with arbitrary pore-size distributions based on a previously developed theory [Yamamoto and Turgut, J. Acoust. Soc. Am. 83, 1744--1751 (1988)]. A sensitivity analysis indicated that, for a fixed permeability value, arbitrary pore-size distribution seems to broaden the frequency dependency of plane-wave reflection and transmission coefficients. Assuming a single pore-size Biot model, performance of global optimization inversion algorithms was investigated using the synthetic chirp signals reflected form a porous seabed with an arbitrary pore-size distribution. Inversion of porosity, shear modulus, and permeability was primarily attempted by assigning representative values to other Biot parameters which have secondary effects on the plane-wave reflection coefficient within their physical bounds. Perfect agreement was obtained between inverted and true values of porosity and shear modulus. However, estimated permeability values were always smaller than true permeabilty values due to the assumption of single pore size.