White marlins are part of a group called "billfish," a term which refers to predatory fish in the family Istiophoridae. As their name implies, they all have bills that they use to attack prey. But that's not the only thing they have in common; white marlins are all very migratory and are often found in tropical or sub-tropical waters. Other members of the billfish squad include black marlin, blue marlin, sailfish, swordfish and spearfish.