boat towed

Hello to all, This is my first post on treasurenet so please be gentle...My question is about towing a PI detector coil on a sled behind a boat. The wreck I am searching for is in 100-150' deep water and am wanting to detect cannons & anchors etc within my budget (Magnetometers will do the job...

What is your experience with a boat towed PI metal detector coil? How effective is this detection system for locating targets underwater when being towed? How effective would it be in locating large non-ferrous targets such as aircraft wreckage buried in a sandy bottom up to 10 to 12 feet...