So for a ship moving along the Channel in light breezes, a favourable tide could double its speed; contrariwise, when the tide changed the ship could be slowed to a halt, or even be swept backwards.
At the battle of Barfleur, for example, when Shovell's squadron was caught by the flood and dropped anchor, the Sandwich, whose captain had failed to prepare for this, was swept by the tide towards, and through, the French line of battle, who had also anchored; she was exposed to their concentrated fire and suffered extensive damage.
The up-tide fleet would send fireships to drift down onto the enemy, whose only option, if they could not destroy them by gunfire, or fend them off using boats, would be to cut their anchor cables and flee.
Cutting and running could also be used to gain a time advantage when using the tide to escape, but involved the loss of an anchor; in a long engagement, where this could happen more than once, a ship could run out of anchors, leaving it helpless before the tide, or have to sacrifice its cannon to jury-rig a replacement.
Dramatically, this happened to the French fleet during the pursuit after Barfleur; Tourville's squadron, unable to round Cap de la Hague with the rest of his fleet, and with anchors dragging in a strong flood, were forced to cut, leaving them to be swept along the Normandy coast to be beached at Cherbourg and La Hogue.