To move one's body, often the limbs, in an erratic or clumsy way. The last time I tried ice skating, I spent most of the time flailing about and trying desperately not to fall.
flail about
or flail around
v.
To engage in rapid, frantic, undirected movements or activity: The baby cried and flailed about as we looked for the bottle. After I caught the fish, it flailed around in the bottom of the boat.