What frequency for lowrance gen 3?

Fishing from 20-40 foot of water? Trying to get better images and have played with both but can’t really tell. What do y’all use?

For down imaging*

455

800 will give you a better picture, but 455 is like ZOOM.

please post a picture of the output. there are a bunch of people who might be able to troubleshoot for you.
tim