Sea Life, the aquarium that will give people a chance to walk “under” an ocean of marine animals, will open to the public Feb. 20, officials announced last week. Construction on the 36,000-square-foot aquarium is nearing completion at Concord Mills. When open, the attraction will feature 5,000 creatures, including sharks, stingrays, an octopus, seahorses, jellyfish, and other animals.