A surveillance system monitors a monitored vessel containing hidden resources. When activity is determined as occurring within a vicinity of the monitored vessel, an alert is issued to monitoring personnel. Personnel can then obtain a current image of the hidden resource within the monitored vessel. Upon receiving the current image of the hidden resource, a previous image of the hidden resource is retrieved and discrepancies between the current image and the previous image are determined. Responsive to determining that discrepancies between the current image and the previous image exist, an alarm is issued to personnel to further investigate the discrepancy.