Early in my teenage years I had a little tin boat with an 8x8 timber post across the middle seat with downrigger mounts. I would fish Coal with no GPS or sounder and manual downriggers. Eventually I got a 3" humminbird and a battery for it. I would cruise around at 60, 90, maybe 120 feet if I was feeling daring, until I ran my gear up on one of the various reefs. Needless to say I lost a lot of my dads 10lb cannonballs.
The humminbird was a real luxury. I remember fishing Coal with my dad around age 4 or 5 and he would be trying to triangulate the reefs using rockpiles, peaks of trees, mountaintops, and the "white lady" which is the white marker south of shag rock. Everybody used to lose a ton of gear there. One of the reefs (I think the one off Charmer Point) was called the christmas tree. I remember an old fishing episode featuring Tom Davis at Coal Island, I think with Gary Cooper, and the rod goes off or something to that effect and long story short they pulled up an old blue scotty handcrank rigger!
I bet theres some interesting stuff down there, but the current rips through there so fast which might make it hard for a diver. Sorry for rambling lol