I would think that two divers and a sluice hook up with a filter arrangement on a pontoon boat or something similar would do the trick for large areas, although you would probably muddy the waters a bit.
You have to get the stuff by the roots and when you pull it up it fragments and you have to collect all the fragments or each fragment can become an individual plant. Some type of filter has to be used.
I have used the poor mans approach, snorkle gear and a nylon mesh bag, with some success. It is difficult to get all the fragments however. It mostly grows in shallow depths.
There is the chemical option also.
I do burn the stuff I collect...but I don't inhale!
I would be interested in what process the certification agency advocates.