An in-water survey is the process of inspecting a ship's hull for damage, organic buildup or any other abnormality in lieu of a dry-dock inspection. Commonly conducted by divers, the in-water survey can be beneficial in finding and repairing cracks, broken welds and rivet problems as well as simply cleaning the hull of a ship prior to painting. It is normal for a company conducting an in-water survey to take many pictures as well as video of the ship's hull. Commentary from the diver as recorded from inside the diving helmet as the inspection is being made is also used as evidence of the survey's findings regarding hull condition.
A ship must be inspected periodically to investigate the condition of the ship's hull. Damage, organic life and the condition of the paint must be verified through actually viewing the condition of the hull. This can be accomplished in one of two methods: dry-docking — which is costly and time-consuming —, or an in-water survey, which does not require the ship to be removed from the water.
Periodically, a ship is required to go through a dry-dock procedure where the hull is cleaned, inspected and painted. When allowed, the in-water survey allows the ship to be inspected while tied up at dock. This process is much faster and less costly than the dry-dock alternative.
During an in-water survey, a diver will descend to the bottom of the ship's hull and scrape away any organic matter that has accumulated on the hull. A visual inspection of the hull will be taken to determine the condition of the paint as well as the steel. Various tests will be conducted and pictures of the hull will be taken. Both digital and film pictures will typically be taken and given to the ship's owners as well as the investigatory board overseeing the testing.
The ship's propeller and rudder system will also be examined during the in-water survey, occasionally resulting in the polishing of the propeller. This service allows the propeller to slice more efficiently through the water and create better speed as well as better fuel consumption. Occasionally, an unmanned robotic diving machine will accompany the diver to the bottom of the hull. This is done to provide light for the in-water survey as well as a method for carrying the required tools and supplies for the diver. The diving machine will also often film the diver completing the in-water survey.