This study addresses the dynamics and navigability of fluid mud by considering the implementation of a nautical-bottom approach using a combination of several measurement techniques. The Port of Santos (Brazil) was used as the study area. In situ measurements were obtained using acoustic equipment, and direct observations were made through density profiles. Sediment sampling was also performed for grain size and rheological testing. The acoustic data indicated the presence of fluid mud in the inner portion of the canal. In this region, high spatial variability was found, where the fluid mud layer thickness ranged from a few centimeters to nearly 1 m, depending on the sand content. In addition, differences of up to 1 m were observed during the tidal cycle. The rheological tests revealed an increase in the yield stress toward the inner portions of the port. Coupling the density profiles with the rheological data allowed the estimation of a potential draft increase of up to nearly 1.5 m, depending on the location, nautical depth criterion, and tide condition.