Semi-submersible

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Semi-submersibles are a type of ship that can partially sink into the water to become very stable. They use ballast tanks that take in or pump out water to lower or raise parts of the hull. This partial submersion creates a wide, steady platform that helps them lift heavy loads or work offshore in rough seas. Some semi-submersibles are self-propelled and can move from place to place.

Two common kinds are:
- Semi-submersible crane vessels (SSCVs): These have giant onboard cranes to lift and place heavy equipment, such as offshore structures or large modules.
- Semi-submersible rigs and platforms: These float in the ocean but are stabilized for drilling or producing oil and gas.

There are also semi-submersible heavy-lift ships designed to carry very large modules. They combine ballast control with powerful cranes to load and unload big items.

In short, semi-submersibles are specialized, partly submerged ships that stay steady in the water, making them ideal for carrying, lifting, and installing large offshore projects.