What does the abbreviation SI stand for in light lists?

In the context of light lists, the abbreviation SI stands for "Sailing Instructions." This term is commonly used in navigation to refer to guidelines that vessels must follow in a particular area, ensuring safe and efficient travel through various water routes. Sailing Instructions typically contain important information about navigation, hazards, and operational procedures that are crucial for mariners.

The other options, while they may relate to maritime terminology in different contexts, do not accurately represent what SI means in the context of light lists. Understanding this terminology is vital for anyone studying navigation and performing duties as a captain, as it reflects the specific instructions and data that guide vessel operations.