Nick,
I'll be updating the 'Ponds and Marshes in 20 minutes' thread.Later this month with a rice paddies hack in under an hour.
It's just a case of re thinking your starting point and using clear acrylic as the base material.
These marshes are as low tech as you can get nothing more than a piece of paper , old CD case's,and grass tufts.total cost £4 for all three.
The lighting doesn't help the picture (reflections hide the implied depth of the water effect.)
But it should give you a rough idea of how easy it is to make rice paddies.
Mark.