The physical features of the seabed, including its shape, depth, and the presence of underwater obstacles such as rocks, reefs, and wrecks. It also encompasses the characteristics of the coastline, such as the presence of cliffs, beaches, and estuaries.

Accurate knowledge of marine topography is crucial for safe navigation, particularly in coastal waters and areas with complex underwater terrain. It helps mariners to avoid hazards, plan optimal routes, and conduct safe anchoring and mooring operations.