Welcome to Ottawa
Which dive shop to use depends on where you will live in town.
In the westend you have The Dive Centre in Stittsville and Kanata Diving Supply in Kanata
In the South you have Divers Warehouse.
Centrally you have Burtons Dive Service, Sharkys and Dolphinos.
In the East you have Adventures in Diving (although Burton's is also east).
Ottawa divers also use Cornwall (Ron's Scuba) and Brockville stores (Sea'n'Sky, Dive Tech and Dive Brockville)
Over the years I have used every store listed above. Some are better than others. I'd recommend that you visit them to make up your own mind. I'll give you my opinions if you want them. They all have webpages. Most run weekend charters as well as Wednesday night fun dives in the summer.
The other thing you might want to check out is independent clubs. There are two active independent clubs in town. They are Forces Sub Aqua Club (FSAC) and Ottawa Beavers Scuba Club (OBSC). A web search will guide you to their web pages.
There is also an active chapter of Save Our Shipwrecks (SoS). They offer underwater archeology courses from time to time.
A good point to start is
www.ontariodiver.com It has links to most if not all of the above.
Enjoy
GDI - AFAIK none of the current Ottawa dive stores have their own pools. The only one that did went bankrupt 7 years ago.