What is the purpose of showing submerged portions in hydrographic surveys?

The purpose of showing submerged portions in hydrographic surveys is primarily to provide critical navigation information. Hydrographic surveys are essential for understanding water bodies' depths, bottom contours, and any submerged features that may pose a risk to navigation. Accurate representations of these underwater areas help mariners identify safe routes and avoid obstacles that could lead to accidents or damage to vessels.

By including submerged portions in these surveys, navigational charts become reliable tools for ensuring safe passage for all types of watercraft. This information is crucial for both commercial shipping routes and recreational boating, as it helps navigators make informed decisions about safe navigation practices based on the specific conditions of a water body.