Undine Weaponshaft

Source Advanced Race Guide

Undines incorporate a unique design when crafting shafted weapons such as quarterstaves, spears, and tridents. Instead of a solid shaft, the weapon is built around a pipe of wood or metal, with the butt end sealed and the front end left open. As a full-round action, an undine can make a single melee attack with the weapon and use her hydraulic push spell-like ability against the target of that melee attack. The weapon otherwise functions like a standard weapon of its type, and can be made of special materials (such as mithral or adamantine) and masterwork quality.