The vast majority of tourists take a ‘tour’. This consists of a morning shuttle bus from their hotel or an agent in central Hanoi to a Halong Port controlled by a mafia that basically only ships people to Cat Ba Island. This gives you the least possible options but can be an easy alternative for time-short tourists.
It is best to avoid beaches and swimming until you get to the islands: depending on the winds, the beach water can be a varying combination between a garbage dump and crystal clear water.
The bay consists of a dense cluster of some 1,600 limestone monolithic islands each topped with thick jungle vegetation, rising spectacularly from the ocean. Several of the islands are hollow, with enormous caves. Hang Dau Go (Wooden Stakes cave, map) is the largest grotto in the Ha Long area.
To the north there is the neighboring bay Bai Tu Long Bay (map) with similar scenery and fewer tourists. Cruises to Bai Tu Long Bay leave from Hon Gai wharf (map) in the city of Ha Long.
There are two bigger islands, Tuan Châu (map) and Cát Bà (map), that have permanent inhabitants, as well as tourist facilities including hotels and beaches. There are a number of beautiful beaches on the smaller islands.