At first watch these insects a long time, to get to know their behavior. Second: get up early in the morning. The larva come out of the pond in the break of dawn. Third: step into the water, sit down and wait with a lot of patience. - My rubberboots and my pants were wet - but it doesn't matter. - At least: you need good luck!
FrikoBel
And sharp!
Darknesse
SiKa