Not sure about the fish finder idea, with all those units in the water pinging at different or the same freqs, the acoustic noise levels on the surface units would be insane.
I like your plan though, shipwreck search that is, I have included all my contact info below, I might be able to help you out a little.
-------------- Original message --------------
From: Recon1st@aol.com
Craig, the tether has bothered me from the beginning. I will be looking for unknown shipwrecks
etc. in Lake Superior, as my main object of exploration. I have been planning on running as
far off the bottom, as water conditions will allow. And one problem in these waters, is nothing
deteriorates. The hemp rope etc. that went down 100yrs ago is as strong as ever (scary) I have
even thought about putting cutters all over, to hack my way free.
From what I can find out water clarity is exceptional in open water on Superior, so was
hoping to stay at least 30' up with forward sonar for obstacles.
For initial cost concerns, wouldn't an array of small inexpensive fish sonar's give tracking data
to the surface support boat. Naturally it would have to be many to give direction, but these
can be purchased for a few hundred and I think should do the job. Look kinda crazy with 8
or so fish finders on the bridge
Also the communications are a concern. I have seen quite expensive dive types that are
not very good and 350' working depth is a problem. Do you know of an inexpensive solution
to the communications?