Is there a way to found out the depth of ur lake without a depth finder? I have been trying to google maps, but had no luck at all.

search for bathymetric maps for whatever state or water body you are wanting to know

oops.. I misread the question, i thought you were trying to use google maps to find lake depths

I fish a shallow lake. Drop the lure to the bottom, bring it up and compare it to the length of the rod.

Get a lure that sinks approximately 1 foot a second, cast and count it down. Not exact but close.

That works, how do I found out which lure drops 1 foot per second?

Tie a weight of some sort to a length of rope marked at specific intervals with a permanent marker. In my part of the world there is little need to measure beyond about 30' other than curiosity. Drop a marker buoy on a known depth, and play around with various baits to get a feel for the rate of fall.

A C-rig is a very good bait for finding depth, bottom contour, structure, and cover. Within a few casts you can begin to get a mental picture of the bottom and the shape of a point or hump. You can verify your findings with a couple of depth readings in key spots. Marker buoys are essential to this process IMO.

Fishing without electronics is a pain for those of us who take them for granted. When I don't have them it forces me to pay closer attention to visible clues to bottom contour and structure, and what my bait is doing. That's not all bad. Good luck.

That works, how do I found out which lure drops 1 foot per second?

Some sinking lures will give you a fall rate somewhere on the package. I'm pretty sure countdown Rapalas have their fall rate in the packaging.