Abstract: Techniques for imaging a subterranean formation include activating an acoustic energy source that is at least partially submerged in a volume of liquid on or under a terranean surface; based on the activating, producing acoustic wave energy that travels through the volume of liquid and to a subterranean zone below the terranean surface; receiving, at one or more acoustic receivers, reflected acoustic wave energy from the subterranean zone; and generating, with a control system, data associated with the subterranean zone based on the reflected acoustic wave energy.