I assume you know why most Creationists avoid canopy theory: because to read Genesis 1 consistently with modern science the "waters above the heavens" must be a layer of water at the edge of the observable universe and "the heavens" refer to outer space.
The alternative theories I know of are:
1. That Earth ran into a patch of interstellar water and got drenched.
2. Hydroplate theory: Earth was originally created with a layer of water underneath a "cap" of granite worldwide, and when the Flood occurred the water broke loose.
3. Runaway subduction: I only know this as a name; I'm not sure what it involves (pseudo)scientifically.
4. Goddidit-too-bad-for-those-faithless-geologists.
And then of course there's the whole "local Flood-global myth" idea but I'm assuming that's not what you want.