I believe she's dragging already, and even if she isn't she would pull her head under water with so short a rope when the sea gets up.

We'd better get out the oars and row to shore, if we can, before the sea gets worse." The lads got up and looked round, and their faces grew pale and somewhat anxious as they saw how threatening was the aspect of the sea.

They had four oars on board, and these were soon in the water and the grapnel hauled up.

A few strokes sufficed to show them that with all four rowing the boat's head could not be kept towards the shore, the wind taking it and turning the boat broadside on.
"This will never do," Frank said.

"I will steer and you row, two oars on one side and one on the other.