The shot in the water looks more like the thumb is moved to the top of the stick while your dryland examples show the thumb staying on the inside of the stick. You can't get the throwing motion with your thumb on the inside unless you have triple jointed thumbs or something and even Liam's are only double jointed. Most of the videos with the big inside flicks are with the thumb on the inside and you see the stick getting pulled quickly into the body on the follow-through. I suspect your shoulder or elbow would/could get wrenched pretty good if you tried a sideways flick with the thumb on the inside.

As was discussed in a previous thread on inside flicks the thumb on top is a different shot than the big high flick with different mechanics and is much easier on the body as it is a more natural throwing motion and doesn't require the strength of the high inside flick.

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