The obvious sports one would expect to find in Bali is of course Surfing. And there is planty. In fact, Bali is world renowned for its surf and surfers from everywhere who flock to Bali to enjoy the glassy tubes.
A word of warning
When surfing, it is wise to be well protected from the sun and the currents and use the buddy system whenever you go out. The most popular spots are: Kuta and Legian beach which is hollow barrels over sand bars, and Uluwatu, a very difficult left hander for experienced surfers only. Other spots include Canguuu and Medwi, which is north of Kuta. During the right time of year, you can find a right hander off the coral reef on the Sanur side.
Making For The Breaks
There are many breaks on the outer islands including Lomboc and Nusa Lembongan. You can rent boards in Bali along Kuta beach(better to rent from shops) and there are shops in the Kuta area selling boards, as well as a surf school. May through September is the Dry season and usually the peak surfing season. Water temperatures are always around 80degrees so only board shorts are required.
I first traveled to Bali in 1974 to go surfing when very few Balinese surfed and few Aussies were there. My favorite breaks are: Uluwatu, a reef break very a hallow and fast left; Kuta Beach is a beach break perfect for beginner surfers as well as experts. The waves are short but you don't have to paddle out very far to reach the break. Padang Padang and Balangan beach are also reef breaks,on the Bukit peninsula, but only for experts;Canggu is a more isolated beach break good for beginners and further to the west is Balian, a river mouth with a sand bottom. Nusa Dua and Sanur beach are both reef breaks but better in the Wet Season October through April.