In Gary Paulsen's The River, Brian does not literally try to drown Derek, but he does feel tempted to because of his state of exhaustion and fear.
After Derek gets hit by lightning, Brian decides that the best way to try to help Derek survive is by building a raft and paddling up a river to where Brian believes a trading post is located, based on a map Derek has that turns out to be inaccurate. Paddling the raft is much harder than Brian could have anticipated because, with each bend of the river, the raft gets stuck, and Brian must free it. In addition, Derek's weight is extremely heavy, and the more soaked with water the raft gets, the heavier it gets. Brian knows he must paddle without stopping if he is going to have a chance at reaching help in time to save Derek. Though he takes a ten minute break each hour, by nightfall, he is so exhausted he starts hallucinating and soon falls asleep. When he wakes up, it is still dark. His hands are covered in blisters, but he resumes paddling nonetheless. As he paddles, he begins hallucinating again. As he hallucinates, he can't help but feel tempted to think how much easier it would be to get to safety if he was no longer carrying Derek. To justify his thought, he grows angry thinking about how stupid Derek was to stand up during a lightning storm, allowing himself to be hit by lightning:
He was dumb enough to rise up and get hit by the lightning, and he should be gone. (p. 107)
It's at this point that Brian, in his exhausted, hallucinogenic state of mind, begins picturing himself dumping Derek off the raft and leaving him to drown. However, he fights his urge, knowing his urge is just a part of his exhaustion and fright. When daybreak comes, his hallucinations go away, taking his temptation to be rid of Derek along with them.