I usually view SI/chart at the same time to give me reference of where my boat is in relation to contour lines or shorelines...

When I see interesting structure on SI.... I cursor over the structure on the SI image and drop a waypoint at the point where it "seems" the structure is intersecting the bottom....

Then, when I hit the "Mark" button... The blue dot waypoint immediately shows up on the split chart view...

I can then goto to the waypoint now or later depending on the circumstances...

Rickie