With an apparatus to collect the gas, another tool is needed to plow the bottom of these shallow waters. A simple tool such as a hoe is perfectly suited for the job. Easy to obtain and use, available everywhere. There is no special technique needed, just plow through the plomp at the bottom of the ditch in order to release the gas that is contained by it.
As it turns out, there is truly a source of fuel on the bottom of the water. By burning it, energy is released which can be seen in the form of a flame.