Like all Mandalorians, Fett wears virtually indestructible beskar armor. Although he still bears its scars, this protected him from the worst of the sarlacc's acid. Crucially, his armor also gave him the tools he'd need to escape from the creature's grizzly innards. After coming to, Boba used a stormtrooper's oxygen tank to take a deep breath of air. He then used his wrist flamethrower to carve a path to the surface.