Answer: Diamond shaped regulatory marker.
Explanation: The regulatory markers are those symbols that are used in order to guide us about any particular place. It warns about the area, how the situation could be, how dangerous it could be, and what are the things that we are not suppose to do. So these informations must be carefully noticed and obeyed.
In order to warn about a rock or any other underwater health hazardous situation, a diamond-shaped marker is generally used in which the diamond shape is made of orange color and the writings are done in black ink.
