The word 'daunt' originates from around the 1300's. It was derived from the French (appropriately enough in this instance) danter, a variant of donter meaning 'be afraid of, fear, doubt' (http://www.etymonline.com/index.php).
In this original context, following a three hour swim today, I reflected on the fact that I would have to do that same swim more than FIVE times in order to successfully arrive on a French beach.
I think that to label such a task as 'daunting' is fully justified in this instance.