Some people think GPS is radar. It is not!

GPS tells you where you are on the globe, period. "Global Positioning System" And that is within a plus or minus range of error.

If you have a gps with a map overlay, that shows someones calculation of where "some" points of interest were at a "given" time, like the shoreline or shoal.

If you run fast at night or in the fog using "only" your gps for navigation, you are endangering your live and the lives of others. That is not navigation. Please use your eyes for navigation and the gps just to let you know where you are on the lake. If you can't safely see in front of you in order to stop quick enough if you saw something you are going too fast.
In dense fog that is idle speed at tops. If the bank is indistinguishable from the water you need to slow down.

GPS will not show a boat with its lights off in the middle of the lake. It may not show a bridge pier, it may not show an island. If you want to be able to see those things you will need to get radar. Radar will show the lake banks, floating logs and everything else.

At night barges use gps, radar and then at critical points huge headlights to see if everything matches up in the real world.

Running a lake at night or in fog using nothing but GPS is playing a very dangerous video game.