Coral reefs, wrecks and excellent water visibility make diving and snorkelling a popular activity in Bermuda. Bermuda is particularly known for its wreck diving, with about 400 to choose from and many are in shallow waters and so easily accessible. The paddle steamer, the Marie Celeste, is one of the prettiest sites, while the Hermes, an undamaged freighter, is one of the most popular wrecks to see. Helmut diving is also available for those who either can't swim or are not qualified to dive and want to experience the underwater world. Snorkellers will enjoy the colourful reef fish and easily accessible sites. The beach at Church Bay is particularly good with an offshore reef and lots of fish, while Tobacco Bay Beach has calm, shallow waters and is sheltered by limestone formations attracting a variety of tropical fish. Many companies offer boat tours to some of the best sites that cannot be reached from the shore.