For movement:
* Controlled: This suggests a deliberate and precise motion.
* Steady: This indicates a stable and consistent movement.
* Graceful: This implies a smooth and elegant motion.
* Skillful: This suggests a movement done with expertise and proficiency.
* Precise: This emphasizes accurate and focused movement.
For effort:
* Effective: This means achieving the desired result.
* Productive: This suggests yielding positive results.
* Successful: This implies achieving the intended outcome.
* Efficient: This means using minimal effort to achieve maximum results.
For communication:
* Clear: This indicates a message that is easy to understand.
* Articulate: This implies well-spoken and fluent communication.
* Precise: This suggests communication that is accurate and detailed.
The best antonym will depend on the specific context in which "flailing" is used.