Some work cannot be done while the ship is afloat. A drydock is a narrow basin that can be flooded to admit a vessel and then pumped dry so that the entire hull is exposed for inspection, cleaning, painting, and repair.

Floating drydocks and graving docks both serve the same purpose. Blocks are arranged to support the ship’s weight according to its docking plan. Once the water is gone, workers can reach the shell plating, sea chests, propellers, and rudders that are normally underwater.

Drydocking is scheduled for surveys, coating renewal, and major repairs. Time in drydock is expensive, so work is carefully planned. Undocking requires refloating in a controlled sequence so that the ship lifts evenly and clears the blocks safely.

• Basin that can be drained to expose a ship’s hull
• Used for inspection, cleaning, and underwater repairs
• Supports the ship on carefully placed blocks
• Critical for surveys and major maintenance