Hakon meant to pen them in some stretch of the river which the pilot knew, and there deal with them.

It was said to be a deep reach with a bar at its head, beyond which no ship might pass until high water.
Suddenly there came a shout from the men forward, and the pilot cried to the oarsmen to cease rowing.

Heidrek's second ship had gone aground.

We could see her crew trying to pole her off, and Hakon asked if we could reach her.
"Not by five score yards," answered the pilot; "but see what happens." I suppose that he knew the Irish ways, for he had hardly spoken when somewhat did happen.

Out of the fringe of thicket and forest along the bank of the river swarmed the Irish, with yells and howls which reached us plainly, and flung themselves into the water to wade out to the ship.