The frequency-domain reflection coefficient contains high information content on seabed properties. In addition to the usual angular domain features of the critical angle and the angle of intromission, the frequency-domain reflection coefficient exhibits Bragg resonances from up- and down-going waves in individual layers and between individual layers. It is the Bragg resonances that contain the highest quantitative seabed information. By using a full-physics forward model (the Sommerfeld integral), a sophisticated and causal sediment acoustics model (Viscous Grain Shearing theory), and a trans-dimensional inversion framework, high resolution (vertical and horizontal) estimates of seabed geotechnical and geophysical properties can be obtained along with rigorous uncertainties. The seabed properties are compared with independent (i.e., not used as a priori information to constrain the inversion results) core measurements. The two measurements of the seabed properties generally agree quite closely.