Abstract from the official IHO web site

Celebrated on 21 June, World Hydrography Day is designed to raise awareness about Hydrography and how it plays a role in improved knowledge of the seas and oceans.

The theme this year is "Hydrography - contributing to the United Nations Ocean Decade".

The goal is to highlight how hydrography as an applied science supports the sustainable use of the oceans. This can include how up-to-date surveys and data can be used for initiatives for the protection of the marine environment, coastal zone management, marine protected areas, marine spatial data infrastructures, renewable energies, and all other components of the blue economy.