Arborists use manual pole saws. Some telescope to 21' or 22'. Silky Hayate, Silky Hayauchi.
We also use Jameson 6' fibreglas poles that snap together. 3 sections of a Jameson with the pruning blade and hook on the end could do it for you. Or the Silky saws.

Maybe you would have luck contacting a tree service company and asking for help. We rescue cats, kites, drones from trees. I'd certainly come out to help a pond owner with a plugged pipe.[align:right][/align]