Investigations on the acoustic properties of marine sediments have been carried out on wide range of core samples from the Australian continental shelves over a wide range of frequencies. In situ measurements in marine sediments are providing better data for characterizing the propagation of acoustic signals in shallow water environments. An in situ acoustic probe has been designed and used to measure the p-wave velocity at 50 kHz using pulse transit timer. The transducer probe is inserted about 100 mm into the sediment with minimum distortion, the transmitter-receiver distance being about 150 mm. The dilatational velocity measurements were found to be of acceptable precision between those of in situ and laboratory measurement. Four sets of three matched piezoelectric transducers each have been mounted in colinear frames to enable measurements of sound speed ratio and attenuation constant at higher frequencies in the laboratory. The experimental and theoretical results were in good agreement and well fitted to mathematical models based on Biot--Stoll theory.