A large range of geophysical processes can be detected at long range using the low-frequency sounds generated. Here we consider an important case: an object like a rock or ice shelf falls into water to generate an infrasound, which can be received at large distances. Neglecting the small-scale splash effects, which would generate a higher-frequency (audible) sound, we consider the water motions with scales of the order of that of the object (say, 100 m). It is shown that vertical displacements of water surface having the same scale are, along with surface waves, able to radiate infrasound with significant intensity both in air and water. Some characteristics of this radiation are considered. Also, parameters for projected laboratory modeling of such processes are estimated. Except for work on small drops and other small objects there has been little work on this question and almost no work including sound measurements in air as well as in water. We know of no research addressing large objects. The motivation for this study derives from possible potential value in remote sensing of ice break offs and meteorite impacts.