As cray mentions ... Drop a waypoint on the interesting item ...

This is a good time to have the preset buttons set to views that will actually help you zero in on structure that was marked in the SI view ...

Have 1 of the preset buttons saved as Chart/SI ...
Have 1 of the preset buttons saved as Chart/Sonar ...(Sonar Beam Select menu set to 200kHz/83kHz to utilize the larger 60° 83kHz cone) ...

After repositioning the boat to pass over the newly created waypoint ... be watching the Chart/Sonar view ...

As soon as the brush enters the 2d cone (and shows on the display) ... Toss out a marker buoy ...

Immediately hit the Chart/SI preset button to see which side of the boat you just passed by the structure ...

Now you know which side of the boat the structure is on AND the structure's proximity to the marker buoy ...

Drop another waypoint on the SI view if the previous waypoint is off by a sizable amount ...

Rickie