Digital delay and sum beamforming is the promising technique for underwater 3D acoustical imaging. Even though time domain delay and sum beamforming is widely used for medical ultrasound imaging, it is hardly used for underwater acoustical 3D imaging. The conventional narrowband transmit coupled with the computational complexity required for the implementation of interpolation filter is the major reason for that. However, with the increasing popularity of wideband and ultrawideband transmission for achieving high resolution imaging and with the availability of efficient software interpolation libraries in modern computing systems, the computational time required for frequency domain beamforming appears to be more than that of time domain beamforming. Thus, through this work, we have attempted to compare the frequency domain vs time domain delay and sum beamforming for wideband underwater 3D acoustical imaging. The simulation findings demonstrated that time domain DAS beamforming is faster, computationally effective, memory-efficient, and offers somewhat superior image quality.