+ Sand tends to move. Only use it if you can be 100% sure that water won't run under you pool. Usually that means you have an almost flat yard that never has runoff move across it during heavy rains. Limestone sand is OK.

+ Heavy plastic (or the black/silver tarps) is OK, but trim it so that it does NOT channel water under the pool.

+ If you can don't buy the pool till the grading is done.