forgive me if this has been asked previously, did a search to no avail.can you not mark a spot on the sounder while running once you've passed the spot?
you probably need a heading sensor? so it knows which direction you passed over it.
No heading sensor needed. The unit saves the tracks/position synced with the sonar screen. Pause the sonar, touch the spike or object, save as waypoint or navigate to. This by far is my favorite function.