World Hydrography Day (WHD) is celebrated annually on 21 June. It was first introduced in 2005 by the International Hydrographic Organization (IHO) and adopted by the United Nations General Assembly in Resolution A/60/30.

International Hydrographic Organization and its full member states have celebrated WHD since 2007, through numerous events, with the aim of informing the wider public of the importance of hydrography for many marine and coastal activities. Special emphasis is on the activities that contribute to enhanced hydrographic data coverage of marine areas, as well as the initiatives and joint projects whose results improve safety of navigation, protection of the marine environment, planned management of the coastal area, establishment of a marine spatial data infrastructure, as well as the latest technologies applied in the field of hydrography.

This year's theme is “Hydrography – contributing to the United Nations Ocean Decade”, which highlights hydrography as an applied science that supports the sustainable use of the oceans. The United Nations has proclaimed a Decade of Ocean Science for Sustainable Development (2021 – 2030) to support efforts to reverse the cycle of decline in ocean health and gather ocean stakeholders worldwide behind a common framework that will ensure creating of improved conditions for sustainable development of the oceans.

Hydrographic Institute of the Republic of Croatia has recognized the crucial role of the sustainable use and preservation of marine and coastal ecosystems and their biological diversity, to which it contributes through participation in different initiatives for the protection of the marine environment, coastal zone management, marine protected areas, marine spatial data infrastructure, renewable energies, and all other components of the blue economy.