History of the Peloponnesian War

There was also some skirmishing in the harbour about the piles which the Syracusans had driven in the sea in front of the old docks, in order that their ships might he at anchor within them, and the Athenians might not sail against them, and injure them by their charge. For the Athenians having brought up to them a ship of ten thousand talents burden, carrying wooden towers and screens, from their boats fastened ropes round the piles, and raised them with windlasses, and tore them up, or, diving down, sawed them in two.

The Syracusans plied their missiles on them from the docks, and the men on the ship of burden discharged theirs in return; and at last the Athenians removed the greater part of the piles. But the most dangerous part of the stockade was that out of sight:

for there were some of the piles which they drove that did not rise above the surface of the sea, so that it was dangerous to approach, lest any one, through not seeing them beforehand, might strike his ship on them, as on a sunken rock. But even in the case of these divers went down and sawed them off for a reward; but the Syracusans made, notwithstanding, a fresh stockade.