The Aktirak is a stone vehicle, carved into the shape of a hammerhead shark, that is powered by the energy components possessed with the crystal shards from the Heart of Atlantis. They are the primarily transportation vehicles with no weapons, unlike the similar Ketaks.
Aktiraks are generally faster than Ketaks, but are more susceptable to damage. It is unknown whether Aktirak does or does not equip energy blast as Ketaks and the Leviathan. But at the end of the film it was still working with the Martag.