What were main events? and Who were main characters?

Four Atlanta businessmen, named Lewis (Reynolds), Ed (Voight), Bobby (Beatty) and Drew (Cox), decide to canoe down the Cahulawassee River in the remote Georgia wilderness, expecting to have fun and see the glory of nature before the river valley is flooded by the construction of a dam. Lewis, an experienced outdoorsman, is the leader. Ed is also a veteran of several trips but lacks Lewis' machismo. Bobby and Drew are novices. Check out the summary in the source-link. It gives you the basics.