For lots of DPV diving you should connect with Dive Tech in Mallorytown. They scoot the St Lawrence weekly from what I've heard.
Not being near the St. Lawrence we dive scooters usually when the dive calls for it. So if we need to go far for something, survey a large area, if we plan on towing something or we need to spend a lot of time somewhere and don't want to waste it traveling. typically we scoot Wiarton to get depth or Tobermory.
As for "after season" diving, we dive a local quarry near Cambridge weekly. Call Groundhog Divers in Kitchener to arrange for passes and get on the list for a schedule. You can connect with other divers and plan dives with them. There are several in our group from your area. Half of them dive a fair amount around Barrie.
We host an annual New Year's day dive there. But you can find those closer to home in Barrie or Humber Bay park if you like. THose considers are often more windy and exposed, but they are free (for the cost of parking.)
We host ice diving courses at the quarry when we have enough students. And we host ice divers there weekly when the ice can support the weight. When ice is thin we host cave divers who use lines to navigate under ice. I enjoy under ice cave diving quite a bit. We've found some novel ways to stay warm for those too.
Finally, there is the KW Scuba Divers facebook page that arranges a monthly supper get-together for divers to chat in person. It's the 2nd Tuesday of the everymonth at a restaurant in Kitchener Waterloo. You'd be welcome there.
