Operational guide · Certification & surveys

Bottom Survey and In-Water Survey (IWS)

Cargo and passenger ships follow distinct bottom-inspection regimes; an ordinary IWS depends on Administration/RO acceptance and UR Z3 and is not Extended Dry-Docking.

bottom surveyIn-Water SurveySOLAS Chapter Iship's bottom

Operational Explanation

Cargo and passenger ships follow distinct bottom-inspection regimes; an ordinary IWS depends on Administration/RO acceptance and UR Z3 and is not Extended Dry-Docking.

Regulatory Reference

SOLAS I/10 cargo; SOLAS I/7 and HSSC passenger; IACS UR Z3 general class bottom/IWS; Rec.133 only for EDD.

For passenger ships, HSSC 2025, 5.10, normally specifies at least two dry-dock inspections in five years, no more than 36 months apart. An authorised reduction to one for eligible non-ro-ro ships sets a 60-month maximum; the other annual inspections remain due. From age 15, special consideration is needed before crediting an afloat inspection. IMO A.1207(34), 5.10.

An IWS must provide information normally obtained in dry dock. Before confirming it, check visibility, hull cleanliness, area identification and means to examine the required items. Damage or conditions requiring further investigation may necessitate dry-docking: video alone does not guarantee survey credit. IACS UR Z3, in-water surveys.

UR Z3.1.3 requires dry-docking for these examinations of ESP ships aged 15 or over; for other ships of that age it requires special consideration before an afloat alternative. Check category and age before requesting IWS. IACS UR Z3.1.3.

Scope of Application

Cargo: at least two bottom inspections in five years and maximum 36 months. Passenger: annual bottom inspection, normally two out of water in five years; any eligible non-ro-ro reduction needs specific Administration acceptance.

Procedure / How to Complete It

Classify cargo/passenger and survey regime.
Confirm Administration/RO/class IWS acceptance.
Apply UR Z3; use Z10 only for the specific ESP category.
Separate ordinary IWS from EDD and its approvals.
Do not apply Rec.133 EDD to passenger ships.

Practical Example

A cargo ship may replace one inspection by accepted IWS without entering EDD; a passenger ship follows its annual/HSSC regime.

What Typically Goes Wrong

Applying I/10 to every SOLAS ship, using Z10 as the general IWS source, or calling every IWS Extended Dry-Docking.

Common Mistakes Mistake Library

Mistake	Consequence	How to Avoid It
Applying I/10 to every SOLAS ship, using Z10 as the general IWS source, or calling every IWS Extended Dry-Docking.	Non-compliant decision or treatment	Follow the approved arrangement and applicable sources

What the PSCO Checks

Check bottom-inspection dates and credit, IWS reports, flag/RO and class acceptance, open conditions or defects and certificate validity. Distinguish a commercial underwater inspection from a formally credited survey.

Operational Tips

Separate current requirement, class/maker, SMS and voluntary guidance.
Do not improvise tests, thresholds or intervals.
Record deviations and corrective action.

Preparation checklist

Ship type distinguished
Correct I/7 or I/10
UR Z3
IWS accepted
EDD separate

FAQ

Do cargo and passenger ships share one rule?

No.

Is an IWS automatically EDD?

No. IWS is an inspection method accepted for the individual survey; EDD is a separate programme with its own criteria and approvals. An IWS does not automatically extend due dates or intervals.

Which is the general UR?

UR Z3; Z10 only within its ESP scope.

Bottom Survey and In-Water Survey (IWS)

Operational Explanation

Regulatory Reference

Scope of Application

Procedure / How to Complete It

Practical Example

What Typically Goes Wrong

Common Mistakes Mistake Library

What the PSCO Checks

Operational Tips

Preparation checklist

FAQ

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