There are some links regarding dredging:

Efficient "muck" harvest

I'd be interested in hearing responses.

Seems like the main issues involved with dredging using a water pump are: (1) debris clogging the lines and (2) separating the water from the dredged muck and then safely returning the water to the pond.

JHAP
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"My mind is a raging torrent, flooded with rivulets of thought cascading into a waterfall of creative alternatives."
...Hedley Lamarr (that's Hedley not Hedy)