Ca Na is a sleepy fishing village producing fish sauce and reputedly some of the best salt in Vietnam. Several hotels and resorts serving domestic tourism have popped up on the beach along Highway 1A a km out of the town.
Buses going between Nha Trang and Mui Ne can let you out or pick you up on the hotel/resort area.
The town itself is not very big and most things are walkable.
There is a small temple halfway up a hill near the hotels.
Vietnam Scuba Resort offers non-certified scuba. Otherwise just relax and enjoy the quiet beach.
There is a stretch of hotels and motels along Highway 1A, including one run by the Mai Linh taxi and transport company you see all over Vietnam.