I fished with a guide on Smith Mountain Lake who had a thru hull transducer (Marty, this guide knew what he was doing unlike our...ahem...guide up north). That thing was amazing. You max out the ping speed and can pick up marks at near WOT. Granted we were seeing schools of freshwater stripers but I was still amazed at how much detail it picked up. Can't remember the brand to save the life of me. Might have to drop him a line.
Threaded Mode