I'm looking for the title of a rather old fantasy movie. I can remember only one scene vaguely. I believe the story involved 2 (?) men and a woman on a journey and avoiding an evil wizard of sorts. The scene I remember:

One of the men is on a raft rowing on a river, with the lady unconsciously laying on this raft. A snake comes from the water onto the raft, to bite and poison the lady.

That is all I can remember, familiar to anyone which movie this could be?