The correct answer is A) Shortening the tow hawser generally decreases the maneuverability of the tug. This is correct because a shorter tow hawser reduces the catenary (sag) in the line, which decreases the tug's ability to respond to changes in the tow's direction or speed. A longer hawser allows more catenary, which gives the tug more flexibility and better control over the tow. Options B, C, and D are incorrect because: B) Increasing speed usually decreases the catenary; C) The hawser should have sufficient length to allow for catenary, not be taut; and D) The catenary should be sufficient to keep the hawser off the bottom, not just touching it.