a composite bat is formed of a stiff core having a thick sheath of an elastomer such as a polyurethane . the bat can have an oval - shaped handle covered with a high friction grip . the elastomer sheath is resistant to water and oil . the bat is useful to hit and stun or kill fish without rebound . the core can be formed of a pultruded resin - fiberglass composite having good adhesion to the elastomer sheath . the bat can also take the form of a billy club .