What happends to Bombur as they try to cross the river?

Bombur fell into the enchanted stream and fell fast asleep.

Before they could shout in praise of the shot, however, a dreadful wail from Bilbo put all thoughts of venison out of their minds. "Bombur has fallen in! Bombur is drowning!" he cried. It was only too true. Bombur had only one foot on the land when the hart bore down on him, and sprang over him. He had stumbled, thrusting the boat away from the bank, and then toppled back into the dark water, his hands slipping off the slimy roots at the edge, while the boat span slowly off and disappeared.

They could still see his hood above the water when they ran to the bank. Quickly they flung a rope with a hook towards him. His hand caught it, and they pulled him to the shore. He was drenched from hair to boots, of course, but that was not the worst. When they laid him on the bank he was already fast asleep, with one hand clutching the rope so tight that they could not get it from his grasp; and fast asleep he remained in spite of all they could do. They were still standing over him, cursing their ill luck, and Bombur's clumsiness, and lamenting the loss of the boat which made it impossible for them to go back and look for the hart, when they became aware of the dim blowing of horns in the wood and the sound as of dogs baying far off. Then they all fell silent; and as they sat it seemed they could hear the noise of a great hunt going by to the north of the path, though they saw no sign of it. There they sat for a long while and did not dare to make a move. Bombur slept on with a smile on his fat face, as if he no longer cared for all the troubles that vexed them.