The titan is the largest triggerfish in the Indo-Pacific at about seventy-five centimetres, though the eastern Pacific stone triggerfish grows larger still. It digs a shallow crater in sand or rubble, deposits eggs in it, and guards them. The defended space is not a sphere around the nest. It is a cone with the apex at the nest and the opening at the surface, because the fish's concern is anything above its eggs.
The practical consequence is counter-intuitive. A diver ascending to get away stays inside the cone and can remain inside it for a long swim upward. Withdrawing horizontally along the seabed, keeping fins toward the fish, leaves the territory much faster. Dive briefings across the Indo-Pacific give this advice and it follows from the geometry.
Bites are real. The jaws are built to crush sea urchin tests and can cut through a wetsuit and into a finger or foot. Attacks are territorial rather than predatory, and outside the nesting period the same fish will usually retreat. The species also carries a ciguatera risk in some regions, so it is not reliably safe to eat.