That 9x12 tarp made from a painter's dropclothe is pretty versatile. The number of ways to set it up as shelter is amazing - limited only by your imagination.
Most of the time I set it up as a "diamond" shelter, or "plow point" shelter. I tuck 3 feet under so I have a 9x9 square. I then tie one corner to a tree, stake the opposite corner to the ground, and then pull each of the other two corners tight from that back staked corner and stake them to the ground. I then prop a 3 foot stick up in the center to push the tarp up for some headroom. I then spread out that extra part as a little extra groundclothe, roll out my bedroll, and start my campfire just out to the front side a bit. There's plenty of room for one, and can also be used by two if you stretch out right.
We also use it with a canoe to make a lean-to shelter. Prop the canoe upside down and tilted back a bit. Stake or tie one end of the tarp behind the canoe - stretched tight between the two corners on the narrow end. Now tie the other two corners to two of your canoe paddles, and use a bit of rope to stretch them out and down in front of the canoe. There's your lean-to shelter. Extra gear can be stored under the canoe, or you can stretch out and sleep under it if the canoe is large enough. If your paddles are long enough, then the canvas will slope enough to drain any rainwater over the back of the canoe. You can use a couple long poles if your paddles are too short, or you want more "headroom" out front. This was the traditional shelter used by the voyageurs traveling the rivers and lakes back in the 1700's and 1800's, and is still used to this day by many modern canoe campers.
I've also set my tarp up as an A frame type wedge tent - with both ends open (or closed up with another tarp/blanket. Or as that simple lean-to. And I've also just rolled up in it beside the fire. It's just so ... versatile. And, for my historical camping/trekking, it can be documented as being used in those early time periods. Yeah, it is heavier than modern nylon tarps, but that's the price I pay for camping/trekking in that historical manner.
Oops, forgot to comment on that waterproofing. Traditional canvas can and often does "leak" or drip water if you touch it when it is raining/wet. So you do need to keep your bedroll away from touching the sides when it is raining - or it can "wick" water through and into your blankets/clothing. Just one of the known hazards of using canvas when camping.
I hope these humble thoughts help.
Mikey - yee ol' grumpy blacksmith out in the Hinterlands