This flail is created from a writhing ball of tendrils and spines. At times you are sure it moves slightly on its own. It has 8 charges and regains 1d6+2 expended charges each day at dawn.  
Any attack made with this weapon is not affected by water or being underwater. Additionally, as a reaction, you can expend a charge to reroll the attack and take the second result.  
Additionally, any time you hit with this flail you can choose to expend a charge to deal an additional 2d8 Piercing damage.