This is my 50th year in diving & over those years ( of both commercial diving & recreational ), I've found, or have be part of finding, some pretty neat stuff, but I'll focus on the recreational side:
> cremated human remains
> boats, boat motors, cars, trucks, bikes, motorcycles, shopping carts, snowmobiles, kayaks
> wallets, purses, safe deposit box, keys, phones, clothes, drones, picnic tables, cameras, anchors
> old logging equipment, old clay smoking pipes, old china and lotsa old bottles
Here's a favourite from last year...