"Eight turns back into a boy and skips along the surface of the pool as if it were solid ice. When he circles back to us, he begins to sprint before skidding to a stop, sending a wave of water towards Marina."
(Number Six, The Rise of Nine)
Pondus is a Legacy which allows the member of the Garde who possesses it to alter their molecular density. This can allow them to become impenetrable, allow them to phase through objects or even walk on the surface of any body of water as easily as they could on solid ground.
Kopano develops this Legacy not long after he develops Telekinesis. Originally, he is only able to increase his body's density to become hard as stone, triggered by an attack during one of his father's deliveries. This leads Malcolm Goode to believe Kopano has the Legacy of Impenetrable Skin. However, Kopano develops the other side of his Legacy when he phases through handcuffs restraining him and ice on the surface of a frozen lake to save Nigel from drowning.