Endo,
That’s a 778c model unit for sure. Made on February 26th of 2010 on manufacturing line 3, being the 417th unit made on that line on that date. Looks like there have been some software updates for your model since it was made too. Not sure if they will help you with dialing your unit in but they should help with the shallow water readings. You will need to use the PC Connect cables to update your unit though (maybe someone you know or a marine sales store has these and will update your unit).

Could you share the menu changes you made here so others that may be searching could benefit from them?