Humminbird Ultima - Manual (Page 18)

6. Using Bottom Lock;
Factory setting; OFF
Bottom Lock provides an up-close view like Zoom,
except that in this case the zoomed view automatically
moves up or down to stay on the bottom. To use this
feature, select BOTTOM LOCK and press ON-OFF.
The range of the display is shown when bottom lock is
on and a "BL" appears by the bottom range number.
This is an ideal feature for finding structure or
locating fish near the bottom.
Remember; If bottom Lock is the last function
selected, you can use the ON-OFF button to switch
Bottom Lock on and off without having to press select.
7. Selecting Fish ID;
Factory Netting: On
When you turn the Ultima on, the unit automatically
sets Fish ID to the On position. To turn the ID feature off,
and display fish with pixels instead of the ID icons, press
the ON-OFF button while within the Fish ID menu. Pressing
the ONOFF button again reactivates the ID function.