You could be hung up on a sandbar. In some cases, the oar does not provide enough power to get you off. If reversing does not work, try pushing the raft. Step off the back and swim to the ladder. Don't press "E" but continue swimming as if you were trying to swim through the raft. Watch Your Stamina! If it gets low, press "E", climb back on the raft and sit down to rest. If you are snagged, you should be able to move the raft enough to get yourself free. May have to push on different parts of the raft's perimeter.