Hey Chris, in Sask there are a lot of big boating spots and I would say the majority of people who have boats also have a cabin at a lake, I would list them off but I don't think they would all fit in the thread.
http://www.sasktourism.com/places-to-go/lakes?WT.mc_id=go8g9&WT.srch=1
Your right that there isn't a ton of lakes in the southern part of the province but there are some, you never have to drive real far to find water, my family have been at Jackfish & Murrey lakes since 1955 and it is rare that I ever miss a weekend in the summer, my grandparents paid $110 for both lots, haha, I bought my own place out there in 2000, it's 176 km from my house to the cabin, there is a creek that joins the two lakes and with both lakes there are about 2600 cabins.
here is a pic of one of the beach's
and a look across the lake
This is my front yard, it's in Cochin on the creek that joins the 2 lakes together.
I love the lake life and can't imagine my life without it, ready for it to warm up here soon so some of that ice starts melting, -33 here this morning,
it's all that everyone I know has been talking about is getting back out to the lakes, I guess my point is it's very popular to have a cabin here, there are also a lot of people that will just rent a camp site for the whole year and leave a camper there, just to name a few of the popular boating lakes, Emma, Candle, Turtle, Waskesiu, Emerald, Blackstrap, Diefenbaker, Christopher, Chitik, these are all within a few hours of Saskatoon and there are a ton more, prices have stayed fairly reasonable because there is so much lake property available but just in the last 2-3 years they have really increased a lot, all the baby boomers are selling there homes in the city to move to the lake and retire and driving prices up, sure glad I got in when I did.