Christmas Island is well known for its biological diversity. There are many rare species of animals and plants on the island, making nature-walking a popular activity. Along with the diversity of species, many different types of caves exist, such as plateau caves, coastal caves, raised coastal caves and alcoves, sea caves, fissure caves, collapse caves, and basalt caves; most of these are near the sea and have been formed by the action of water. Altogether, there are approximately 30 caves on the island, with Lost Lake Cave, Daniel Roux Cave, and Full Frontal Cave being the most well-known. The many freshwater springs include Hosnies Spring Ramsar, which also has a mangrove stand.
The Dales is a rainforest in the western part of the island and consists of seven deep valleys, all of which were formed by spring streams. Hugh's Dale waterfall is part of this area and is a popular attraction. The annual breeding migration of the Christmas Island red crabs is a popular event.
Fishing is another common activity. There are many distinct species of fish in the oceans surrounding Christmas Island. Snorkeling and swimming in the ocean are two other activities that are extremely popular. Walking trails are also very popular, for there are many beautiful trails surrounded by extravagant flora and fauna. 63% of the island is national park making it one of the main attractions to experience when visiting.