As soon as Tzirret lost his balance, Ma'tanza threw herself onto him in an attempt to keep him pinned down. At first, they both ended up under the water's surface, but she pushed him, and therefore herself, closer to the shore so they could keep their heads above water. The siblings had the advantage currently, though it was obvious that neither were particularly trained. Ma'tanza was trying to pin him with her body weight, and had her arms around his torso, on the outside of his own arms in an attempt to keep him from using them. However, she was not using leverage and was simply trying to control his arms through force. Being a werewolf, that would not work for long. Although, if her brother had time to do the same, they could both together have the strength to keep him down, and he was already scrambling towards them. 

[i]"Pin him brother! Keep him down!"[/i] Ma'tanza shouted.