In water survey (IWS)
The survey of hull plating undertaken in the water. The ship is provided with marks placed on the shell to show borders of tanks, cofferdam etc. Hull plating should be cleaned by a diver-operated machine. A remotely-operated underwater TV camera is used to view the ship plating.
IWS can be also applied for checking that the seal assembly on oil lubricated sterntube bearings is intact and for verifying the clearance or wear-down of the stern bearing. For that, an opening in the top of the seal housing and a suitable gauge should be provided for checking the clearance by the divers.