There’s a lot to see in our national parks and historic sites, including some pretty interesting things underwater. Lynn Riddick takes a look at the Submerged Resources Center, the arm of the National Park Service that locates underwater resources – whether sunken ships or planes, old ranches or train tracks, coral reefs or kelp forests -- then documents and interprets them. Always with an eye toward their preservation. And with 3.5 million acres of Park Service land underwater, it’s an immense yet intriguing responsibility.