The first dataset consists of the data to accompany the paper 'Modelling acoustic scattering, sound speed, and attenuation in gassy soft marine sediments' by A. Mantouka, H. Dogan, P.R. White and T.G. Leighton. This paper was published as J. Acoust. Soc. Am. 140, 274 (2016); http://dx.doi.org/10.1121/1.4954753. The second dataset consists of the data to accompany an as-yet unpublished study, which will be entitled 'Acoustic wave propagation in gassy porous marine sediments: the rheological and the elastic effects' by H. Dogan, P.R. White and T.G. Leighton.