Oh dear - another duck disappointment.
Sounds like an inferior leisure model to me, quite possibly made of cheap Taiwanese mass produced generic 'rubber' - actually plastic. The market has been swamped with these and unsuspecting people are fooled into buying them because they look just like the real thing. But when put to the test in demanding wet conditions - they often fall causing disappointment and frustration. They are just not balanced right.
Invest in a decent quality properly engineered duck. Prefereably one that has been properly fitted so it is the right size for you. And don't head straight for dangerous full bath conditions - get used to it in the dry first, then in more controlled sink conditions where an accident won't cause such a problem. Get the posture right, get accustoomed to the way it moves and learn how to handle it.
Don't expect too much of yourself at first - but keep at it!
