A dry dock is a basin, platform or ramp that lifts a vessel completely out of the water so the hull below the waterline can be inspected, cleaned, repaired and repainted. There are four working types — graving docks, floating docks, slipways and airbag haul-outs — and every classed ship must use one of them at least twice in each five-year class cycle. This guide explains how each type works, what actually happens inside a dry dock day by day, and how the terminology is used in shipping.
Answer first: what “dry docking” means in shipping
In everyday shipping language, “drydocking” means the whole planned event: taking the ship out of service, lifting her out of the water at a shipyard, performing the survey and repair works that can only be done with the hull exposed, and returning her to service. The word covers the physical structure (the dock itself) and the project (a “15-day drydocking”). Because underwater parts — shell plating, sea chests, propeller, shaft, rudder — are invisible in service, dry docking is the only moment their true condition is known. That is why classification societies anchor their survey system to it and why owners concentrate as much commercial work as possible into each docking.
The four dock types and how each lifts a ship
| Type | How it works | Typical use |
|---|---|---|
| Graving dock | Excavated concrete basin; ship floats in, gate closes, water is pumped out | Largest vessels; heavy steel and long refits |
| Floating dock | Steel pontoon submerges, ship floats over, dock deballasts and rises | Most common in Indonesia; flexible, movable |
| Slipway | Ship is winched up an inclined track on a cradle | Small and mid-size tonnage; tugs, ferries, wooden vessels |
| Airbag haul-out | Ship rolls up the beach on inflated rubber bags | Smaller craft at simpler yards; low fixed cost |
Each method ends the same way: the ship sits on keel blocks arranged to match her docking plan, with side shores keeping her upright. The engineering differences between the two big-ship options — and when each wins on cost and schedule — are covered in our comparison of graving docks vs floating docks.
What happens inside a dry dock, step by step
A routine docking follows a rhythm that is remarkably consistent worldwide. Day one: docking manoeuvre, the ship settles on the blocks, and high-pressure washing strips fouling off the hull while it is still wet — delay this and the growth hardens. Days two to four: inspection. Ultrasonic thickness gauging maps the steel, sea valves are opened, the propeller and shaft are checked, anodes assessed. From that inspection comes the real work list: steel renewal where plate has wasted below class limits, machining or repairs to the stern gear, blasting and repainting of the hull in a multi-coat system, overhaul of valves, and whatever project work the owner has scheduled — equipment installs, pipe renewals, tank coatings. The final days reverse the sequence: class surveyor witnesses the survey items, tanks and valves are closed up, the dock floods, and the ship refloats. A typical routine docking runs one to three weeks; heavy steel or full coating systems push longer.
Why ships must dry dock: the regulatory clock
Classification rules require the underwater hull to be examined twice in every five-year period, with no more than 36 months between examinations; one of the two must coincide with the special survey that renews the ship’s class certificate. Statutory certificates and hull insurance both hang on that class being maintained, so the docking calendar effectively governs a ship’s commercial life. Some vessels may substitute one docking with an approved in-water survey, and a minority of ship types can enter extended programmes — but for most owners the practical planning number is: a docking roughly every two and a half to three years. How Indonesian yards handle bookings, and which dock type suits which vessel, is set out in our dry dock & haul-out guide.
Dry dock, wet dock, dry berth: untangling the terms
The vocabulary trips people up. A wet dock is the opposite of a dry dock: an enclosed basin where ships float at constant level for cargo work — nothing to do with repair. A dry berth usually means long-term storage of a vessel ashore, common for yachts and laid-up craft, without the survey-and-repair purpose of a docking. Careening, the ancestor of it all, meant beaching a ship on the tide to expose one side of the hull — still visible in traditional Indonesian practice for small wooden craft. And drydocking meaning in a charterparty context usually refers to the owner’s right to withdraw the vessel from service for her scheduled docking — a clause worth reading closely when laytime is money.
What dry docking costs and where the money goes
The dock itself — dock dues, docking and undocking operations — is rarely the biggest line. On a typical routine docking invoice, steel renewal quantities, surface preparation and coating areas, and machinery overhauls dominate; the dock fee is the entry ticket. In Indonesia, routine dockings for small and mid-size tonnage commonly land in the tens of thousands of US dollars up to the low hundreds of thousands for mid-size cargo vessels with meaningful steel work. We publish planning bands, per-GT rates and a worked invoice anatomy in the dry docking cost guide (USD). For a shortlist of Indonesian yards by dock type and capacity, start at the National Yard Register.
Planning a docking in Indonesia? Send us your vessel’s particulars and survey due dates — we reply with suitable yards, slot options and a USD estimate, and can supervise the work owner-side. WhatsApp +62 811-3823-875 · sales@komodoluxury.com.
Frequently asked questions
What is a dry dock in simple terms?
A structure that lifts a ship completely out of the water — by pumping a basin dry, raising a floating platform, or hauling the ship up a ramp — so the underwater hull can be inspected, repaired and repainted.
How often must ships dry dock?
Classed ships must be dry docked twice in every five-year class period, with a maximum of 36 months between dockings; one docking coincides with the special survey. Some vessels may replace one docking with an approved in-water survey.
How long does a dry docking take?
A routine docking for a small or mid-size vessel typically takes one to three weeks. Heavy steel renewal, full coating systems or major machinery work can extend the stay to a month or more.
What is the difference between a dry dock and a wet dock?
A dry dock removes water so the hull is exposed for repair. A wet dock is an enclosed basin that keeps ships afloat at a constant water level for loading and unloading — it has no repair function.