Bobn,
Welcome to the forum. Yes, it is accurate. There are several measurements taking place and understanding the difference between Horizontal Range and Slant Range is important. Here is some good reading:
Slant Range distortions and Calculating Waypoints The range that is Shown on your HB unit is actually called the Slant Range. By know ing the depth and the slant range, we can calculate the Horizontal Range using the Pythagorean Theorem.
Basically, if the Cursor is in the water column, the Horizontal Range is zero. The point you are seeing is actually directly under the boat, even though it looks like its out to the side.
Hope that helps. The important info is in the other post.
Good Luck,
Robert