. >> here at the national aquarium in baltimore, an exciting transformation has taken place. sea creatures that have been here for years were carefully transported to safety. then the aquarium was drained and a coral reef was created. add 250,000 gallons of salt water, exotic sea life from halfway around the world, some really cool lighting, and what do you get? the amazing blacktip reef -- a unique museum experience. with 65 different underwater species, it's as close as you can get to seeing a south pacific coral reef without going to the south pacific. >> coral reefs are like the cities of the ocean. it's an ecosystem that's all balanced. >> to re-create that balanced ecosystem, all the sea life was carefully selected. the only thing that's not really from the pacific is the coral. it had to be man-made. >> coral is actually a living animal. it looks like rock. and it's related to jellyfish, and it actually forms a limestone cavity around itself, so it's basically like the outer edge of the coral is living and building on the limestone skeletons of its ancestors. and the co