One of the largest aquaria in Europe, this South Bank attraction boasts 350 species of fish, everything from British freshwater species to sharks that once patrolled the Pacific. You'll see the bountiful riches of the coral reefs of the Indian Ocean, discover what lurks in the murky depths of the Atlantic and Pacific oceans, and come face to face with an array of eels, sharks, piranhas, rays, jellyfish, clownfish, tangs, and other denizens of the deep. You can ford a freshwater stream into a mangrove swamp to reach an exhibit of a tropical rainforest. The seawater, incidentally, is just normal Thames water mixed with 8 tons of salt at a time.