If you have a boat, there's there are the remains of the Mary Ward just off Craigleith. Not deep, I'm told about 15 feet. I haven't done it yet myself. It's on the agenda for this summer, but I need a very calm day to thread my way in and anchor.
Cedar Hill is fun, drops off quick enough to get some depth.
Also not too far, if you have boat access is the Marquette off the East side of Hope Island. Nearly intact hull of a 135' schooner barge in about 30 to 35 feet of water, an anchor at the bow, capstan, centerboard trunk. Always been great viz when I've been there. Just a bit further North off the lighthouse is pieces of anouther schooner barge, but it's shallower in the 15 to 18 foot range and the ice has broken it up quite a bit. Make a nice second or third dive and you can get an idea how the vessels double planked hulls were built.
I keep a boat in Meaford (just a bit West of Craigleith) and have done some dives on the North side of the breakwall. There are the remains of the original dock, which ran out at least another 200 feet from where it ends now. Lots of rock and cribwork along with other artifacts. Sometimes some fish, last summer we ran across a huge sheepshead (what an ugly fish).