Liquid Robotics in Sunnyvale, Calif., said its PacX Wave Glider made the 9,000-nautical-mile journey in slightly more than a year while gathering data about the Pacific Ocean's temperature and salinity.
The robot has no fuel, but "swims" using energy gathered from ocean waves acting on a submerged keel equipped with a series of fins.
On the robot's upper surface, solar panels power scientific instruments.
The successful ocean crossing shows such technology could "survive the high seas," Liquid Robotics said.
The robot was dubbed Papa Mau to honor Pius "Mau" Pialug, the late Micronesian navigator know for his skill in completing long-distance ocean voyages without the use of modern navigational equipment, the BBC reported.
"During Papa Mau's journey, [it] weathered gale-force storms, fended off sharks, spent more than 365 days at sea, skirted around the Great Barrier Reef, and finally battled and surfed the east Australian current to reach his final destination in Hervey Bay, near Bundaberg, Queensland," Liquid Robotics said in a statement.