What is the reference point for the depth of an oceanic floor profile?

The reference point for the depth of an oceanic floor profile is the water surface. This is because hydrographic surveys measure the vertical distance from the water surface down to the ocean floor and represent that depth with respect to the surface of the water. The measurements taken are often referenced to mean sea level, which is a stable and standardized baseline for determining the depths in bodies of water.

Using the water surface as the reference allows for consistency in surveying and navigation, as this surface is where vessels operate and charts are plotted. It's critical to have a clear point of reference so that depth measurements can be accurately interpreted and compared across different locations and times.