Casting Disaster

New fly rod....big trouble. Tried casting while actually standing in a
stream last night. Two books said that x amount of line should be laying in
front of me before the pickup. This worked fine when practicing on the lawn.
They do not explain what to do when the water's moving swiftly from left to
right, taking the pile of line with it, and you want to fly to end up to the
left. I managed something creative, but the leader & tippet were not exactly
landing gracefully - more of a bunch than a nice presentation. Help.