Complex sentence: The Kamaishi Tsunami Protection Breakwater, long and in depth, was completed in March 2009, and recognized by the "Guinness World Records" as the world's deepest breakwater.
Split into simpler sentences: The Kamaishi Tsunami Protection Breakwater, long and in depth, was completed in March 2009. It was once recognized by the "Guinness World Records" as the world's deepest breakwater.