Any decent swimmer can get to 24'. just be sure to equalize on the way down and blow slowly on the way up.
I have to agree that most lake bottoms are useless muck. Not much chance to get it back if that is the issue.
The drag magnet trick will work, assuming you can find one quite large (normally, these need to be about the size of a brick). they are usually already rigged to a handle, but should be able to pull up a drill.
Assuming fresh water, then dry out well before you attempt to run it. Disassemble the batteries from it if possible to allow drying. I also would use Contact Cleaner or such from Radio Shack or similar to run out any water prior to attempting to run.
If saltwater, use saltaway or similar as soon as you pull it out of the water, then follow with the contact cleaner, complete drying, then let us know.