There are several different routes you need to take in the rapids. 4 to be precise. Each leads to a different candle. You need to raft down the river at least 4 times, and make sure that you grab spare raft repair kits from the soviet guardhouse as often as you need them. Every time you reach a fork in the river, remember which way you chose to go, and the next time through go the other way. Some of the candles are easy to get, just walk up and grab them. Others require clever solutions.