Eventually the area was roped off and Filch, gnashing his teeth furiously, was given the task of punting students across [the swamp] to their classrooms (OP30).
(noun) A long, narrow, flat-bottomed boat used on inland waterways (like the Isis river that flows through Oxford). It’s a kind of pole-boat. As a verb, “to punt” means to push a boat along by a long pole; the punter pushes the pole against the bottom of the river to move the boat.
For those who indicated confusion about what "punt" meant in this context, we recommend the works of the British mystery writer Dorothy L. Sayers, specifically the Lord Peter Wimsey novel Gaudy Night. One of the major scenes of the book features Lord Peter punting on the Isis river with Harriet Vane.