How tall is red seaweed?

Found in the cool waters of the Pacific Ocean Macrocystis pyrifera, better know as Pacific giant kelp, is the world's longest seaweed. Pacific giant kelp grows at .0002 MPH or up to 1 1/2 feet/day making it also the world's fastest growing plant. The overall length of Pacific giant kelp does not exceed 60 meters or just under 200 feet, but even at that length it still is the world's longest seaweed.