Camping in Hainan
It is possible to camp in Hainan both on the beach and in the countryside.
I haven't seen any campsites, but from my personal experience it is possible to camp pretty much where ever you like. It is certainly possible to camp outside of the tourist areas. Most of Hainan, outside of Haikou & Sanya, is undeveloped and rural. So it is not too difficult to find an empty (apart from a few local fishermen) beach or attractive countryside to camp at.
It is possible to buy tents in Hainan if you don't already have one.
Wanquan Lake Camping
Wanquan Lake / River is near Qionghai and about half way down the east coast of Hainan. The spot we decided to camp at is pretty remote and only accessible by boat, so we hired a local to take us across the lake. The area turned out to be perfect. There was a clear river running down between two mountains and thick tropical jungle on either side. The river was broken up by many waterfalls and lagoons. The water was cool and so a great escape from the hot sunshine. It was cool jumping from rocks into the deep lagoons, have a look at some of the photos. This place was beautiful
Camping in TianYa
After the success of the last camping trip we decided it was time for another. An acquaintance offered a trip on his boat to a deserted island just off the south coast of Hainan, where we planned to camp overnight. However things didn't turn out exactly as we would have liked. The boat trip never materialized and instead of relaxing on a small island we spend the day getting lost in random towns while searching for a good spot to camp.