In-water survey instead of dry-docking

Arie van Wingerden

Now that Lagersmit announced Subsea Global Solutions (SGS) as our exclusive U.S.-based service agent, we are also able to facilitate in-water. In-water survey (referred to by various classification societies as IWS, BIS, etc.) is a method of surveying the underwater parts of a ship while it is still afloat instead of having to dry-dock it for examination of these areas as was conventionally done.

Pre-examination in-water survey program

The first step to make an in-water survey possible is to send an initial application to the classification societies’ Ship Safety division indicating the intention to have any ship(s) participate in an in-water survey program.


The ship then must be examined to get an approval of Class Societies Ship Safety Headquarters to get into the In-Water Survey Program. This examination of the underwater portion and fittings of the hull as required by the appropriate regulations can be made by a team of competent divers and technicians in the presence of a Marine Surveyor. The diving company must be approved by the appropriate Classification Society in order to execute this survey.


The in-water survey should provide, for as far as possible, the information on the condition of the vessel’s underwater hull and fittings usually obtained from a (previous) dry docking survey.


One of the other requirements that needs to be checked are the stern tube seals. The report needs to provide information ascertaining that the seal assembly on oil lubricated bearings remains intact and that the clearance or wear down measure of the stern bearing has been verified to be in accordance with OEM specifications. For wood or rubber bearings, an opening in the top of the rope guard and a suitable gauge or wedge should be provided for checking the clearance by the diver.


Please note that in case the Marine Surveyor is not satisfied with the outcome of this first in-water survey or if the condition of the vessel warrants a survey in dry dock this must be arranged by the ship owner. Read our blog to find out which preparations need to be made for in water seal repair.

In-water survey requirements

When you get the IWS notation and you want to conduct an in-water survey, you must send a request to a Ship Safety office indicating information such as date and location of the survey, general information on the diving company and a schedule for undertaking the in-water survey. This survey can be completed UP TO 3 months in advance of the due date. This gives ship ownersflexibility in scheduling this survey.

Did you know an in-water survey should be conducted according to the following requirements?


1. Master’s Statement
At the time of an in-water survey the Master or Owner’s representative should provide a declaration of all suspected or actual damage that has occurred since the previous dry-docking.


2. Survey Site
The proposed survey site should be in a protected location with calm clear water providing good underwater visibility. Visibility is typically greater than 2 meters length. Sufficient visibility shall be available to enable the Marine Surveyor to ascertain if the hull has undergone any permanent setup or set down. Special attention should also be given to the effects of current.


3. Hull Condition
The hull should be clean for external survey and the Marine Surveyor should be satisfied that the method and quality of pictorial presentation is satisfactory and that the information obtained enables a reliable assessment to be made of the condition of the hull. The survey should be discontinued if the conditions or equipment deteriorate to the extent that the transmitted pictures and/or communications are no longer acceptable.


4. Underwater Areas
An examination of the entire vessel below the waterline should be carried out by a competent diver using closed circuit television with two-way communication capable of being monitored by the Marine Surveyor as required.Where practicable the in-water survey should be carried out while the vessel is in Light Operating Condition to facilitate the survey.


5. Above Waterline Areas
An examination of the outside of the shell plating above the waterline and exposed portions of appendages should be carried out by the Marine Surveyor. Means should be provided to enable the Surveyor to accomplish this visual examination.


6. Internal Inspection
Where a defect or damage is detected or suspected as a result of the in-water survey or the Master’s statement, the internal structure should be examined as considered necessary to clarify or confirm the findings. Vessels operating in ice should have the internal structure examined in way of areas which are susceptible to ice damage. In this respect, attention should be given to the hazards associated with entering ship’s tanks.


7. Report
Copies of the diver’s report, pertinent colour photographs and/or video tapes should be submitted to the attending Marine Surveyor and Ship Safety Headquarters for record purposes.

Stern tube seals & ships with iws notation

All our oil lubricated Supreme stern tube seals, capable of doing bearing wear down measurements, are acceptable for ships having an IWS notation. The procedure for doing wear down measurements is basically the same as doing these measurements in dry dock. You must have access through the rope guard if fitted!


Tools for doing these measurements, to know: measuring plug and sliding gage/poker gage, are supplied as standard with new Supreme oil lubricated stern tube seal orders. The maximum allowed bearing clearance will depend upon shaft diameter, lubrication type (oil/water), bearing material and loading. The actual distance measured is less important than the change in distance.


Please be aware that some oil spillage may occur when removing the stainless steel plug and check with relevant national authorities if this is allowed. Our partner Subsea Global Solutions meets these requirements in their locations and in many of their partner locations globally.  We are happy to work with you to support your IWS needs at any time.

More information

As a client of Lagersmit we can offer you in-water surveys via our US-based service agent Subsea Global Solutions. SGS has a dedicated staff situated globally and over the years revolutionized the methods of repair for ships and advanced the methodology used in underwater Marine Construction. With class approved techniques and a highly trained staff in both underwater ship repair and propulsion equipment maintenance, SGS is the clear choice for vessels operating in sensitive environments and on critical trade routes.

Share this article on:

General phone number