Stagger the ends like you would for a brick style wall, and should work well.
QUIKRETE® Tubesand® is packaged into a heavy-duty, water proof, plastic bag that is UV, break, and tear resistant.
I would not recommend them for use INSIDE the pool. The liner inside the bag is extremely thin, and though the exterior bag is more resilient, one small puncture will yield to further damage without much effort. I am currently using about 100 bags outdoors. Some of them are damaged after being stepped on. A few have been torn open by merely picking them up. However, i must note that these bags have been weathered up to 4 months in sun and rain on asphalt.
Why would you want to drive over it? It's designed for adding weight to the back of a truck with rear wheel drive. If you drive over it, it's going to split the package and dump all over the ground.
I had a Ranger with a plastic Bedliner. The liner had two or three sideslots for either 2" X 4" or 2" X 6" cross boards. I set two 60 lb. Quickrete tubular sandbags over the rear tires and sandwiched between the cross boards so the bags would not slide forward or backward. Two bags (120 lbs.) was sufficient.
I bought the prefilled bags for their intended purpose, being winter weight in my pickup bed. I recently opened a few bags to use the sand for another use, and it's basically white beach sand.
Approximately 3 feet I believe