You'd think someone who gets shot at out in the open and turbulent seas would be able to confidently pull off a backflip in her wheelchair.
Sense of balance don't work that way, yanno. It's even the opposite-sailors has less sensitive semicircular canals, or should I say, desensitized from all that rocking.
Also, doing a backflip on a wheelchair involves more than having a great sense of balance. You need strength of the waist to actually drag that wheelchair around in the air.