He sacrificed himself to save the others. Either, he knew if he jumped for that wheel, he wasn't getting back to safety, or he didn't think about it at all and just hastily jumped for it, in anger.
I think he knew it was curtains for him; he jumped to save the gp. There was no way back, the wheel was wet, and he was exhausted from hanging and turning it. He let go, and didn't fight the inevitable. Great characters, all of them

In the novel, after Linda's violent death, the ship started to shutter and pitch. Scott thought the ship was going down and became infuriated that his God would snatch victory away from him. So he abandoned the group and lept into the pool of water and wreckage. None of the survivors looked at it as a sacrifice, just foolhardy. Unlike the film, no one in the group of survivors liked Scott.

He said "You can make it. Keep going. Rogo? Get them through" Obviously he knew he couldn't hang on much longer.

He just suddenly felt like taking a hot bath.