"...You need to learn about missile flight profiles...."
I could address the same remark to you.
"...BTW, do you have any idea what a 3" thick piece of steel, the full length of the ship, and tall enough to defeat a pop-up missile weighs? What are you going to propel it with? Who is going to drive it? What happens to it in heavy seas? High winds? What is to stop a smart-aleck from sneaking a zodiak loaded up with explosives up next to it, and then zipping around it and WHAM?..."
If 70 meters X 10 meters X 7.5 cm, approximately 412,000 kg. This shouldn't be hard for a catamaran hull with enough beam. Of course, if it were a steel skin around a wooden frame, it would be considerably less. It wouldn't be hard to fit it with an autopilot slaved to the mother ship, and programmed to keep it landward of the mother ship at all times.
.50 caliber Browning machine guns are good medicine for Zodiacs.