Thunderbolt cannonballs or Thunderbolt are a highly charged, long-ranged cannonball that cause a lightning bolt to strike where it lands. Thunderbolt rounds are only mildly effective against ship masts and sails. However, they can also cause considerable hull damage. They are Jolly Roger's favourite, as he used them during his invasions of Port Royal, Tortuga, and Padres del Fuego.
They can be purchased at any gunsmith on the main islands and the privateering islands for 12 gold coins (per 25 rounds).