Typically, these camera systems will have heavy duty cabling that allows the camera to be suspended down into the vessel.  Since there is generally not good lighting inside of a tank or vessel, the camera is equipped with lights as well as the ability to Pan, Tilt and Zoom.  This allows for full inspection of every part of the inside of the cavity.

Both Spot and Flood lights are required to match the zoom level the camera is set to depending on how far away the area being inspected is.  These cameras are enclosed in housings that allow them to be submerged up to 100 ft of water while maintaining continuous operation.