Con Dao Activities

Your first port of call should be the National Park headquarters on Vo Thi Sau Rd who can provide you with a useful booklet detailing available trips. Remember that an individual itinerary can be created. Most walks require a guide, and at 100,000D (around $6) for the day, it's well worth it. Some walks can be completed alone, but still require a permit from the National Park - for example, the walk to the top of Con Son's highest mountain, Thanh Gia -- well worth it on a clear day. 
To explore the island, hire a motorcycle for 120,000D (one day) or 20,000D (one hour). A coastal road links the airport to Con Son town and continues 15km beyond until it ends just past the port at Ben Dam. Stop along the way to explore some of the rocky beaches around the cape at Mui Ca Map and Cua Tu. The best beach near town is Bai Dat Doc, a few minutes by bike from the airport side of Con Son. At the other end of town is Bai An Hai, home to numerous fishing boats and not the best place for swimming. Explore further inland and find local people at work in fields of sugar cane and rice paddies upon the backdrop of Con Dao's mountains. 
One of the most spectacular beaches on the island and a fantastic swimming spot is also part of one of the most arduous treks available for tourists. Start by following the beach of Dong Bac Bay, at least 2km long, before diving into the forest, eventually finishing at Dam Tre Lagoon. Snorkelling here is difficult due to the barnacle encrusted rocks, but the friendly ranger station provides lunch and some rice wine energizing you for the way back. At 12km in total, this walk should be done for the trekking rather than the snorkelling. For a much lighter but still interesting walk, try the path to Ong Dung from where the road ends. 
Other activities include trips to the outlying islands. From May to September Bay Canh island is the best place to find the famous turtles of Con Dao. It is possible to stay overnight and see the turtles lay their eggs on the beach at night. Good snorkelling and diving tours can be organized by Rainbow Divers on Ton Duc Thang, but remember that boat trips to the outlying islands may be cancelled due to the weather. Sunday is not a working day for guides -- unless you ask nicely. 
For those interested in the cultural history of the island, a visit to the Revolutionary Museum is essential. Follow this by seeing Phu Hai prison, and Hang Duong Cemetery. The museum can organise a tour of all these sites for just over $1.