1. A method of detecting structural changes to underwater structures comprising: directing from a sensor an acoustic sonar wave toward an underwater structure; receiving by the sensor the acoustic sonar wave reflected from the underwater structure, the acoustic sonar wave having one or more acoustic sonar pulses, obtaining 3D data points from the one or more acoustic sonar pulses of the acoustic sonar wave reflected from the underwater structure, the 3D data points are configured to provide a three-dimensional image of the underwater structure; aligning a sample of the 3D data points obtained from the one or more acoustic sonar pulses of the acoustic sonar wave to a pre-existing three dimensional model of the underwater structure, the aligning comprises estimating a position and orientation of the sensor relative to the pre-existing three-dimensional model of the underwater structure, using an iterative processing loop based on inliers of the 3D data points; generating a change detection model based on the aligned sample; comparing the change detection model to the pre-existing three dimensional model of the underwater structure; and based on the comparison, detecting whether a structural change in the underwater structure has occurred.