My pond has air under it

When the water table rises and pond liners are floating up to the top of the pond, pushing the water out, you think that is air under your liner. Nope, it's water. 
If your pond was built 3" or 4" above grade, the weight of the water in the pond would keep the liner from bubbling up.

Nothing whatsover will keep that liner in place, so don't try putting rocks in the pond. It won't work. 
Here's what to do: Try to raise the edges. Build a levee around the pond and hope that you left enough liner to cover it. You can use most anything to build that levee.

I always use rocks on top of the edge of the liner, curl the liner up and over that course of rocks and then cover the whole sandwich with another course of rocks. You can see the 'how to' with photos at
How to build a pond

For all pond articles catalogued, see Backyard Ponds with the Pondlady