On the night of May 9, a storm was churning across the Southern Ocean, known for its fierce weather. About 400 miles south of New Zealand, a new ocean buoy was doing its job and getting battered by rough seas. Although “rough seas” is probably an understatement.

Around 2 a.m., the buoy measured a 78-foot wave near Campbell Island, the largest ever recorded in the Southern Hemisphere. And since the buoy doesn’t stay on 24 hours a day, even larger waves could have been missed.

The buoy was installed on March 2, and already it’s logging records. Campbell Island, uninhabited except for a population of southern royal albatross birds, is the southernmost extent of New Zealand.

Tom Durrant, a senior oceanographer at MetOcean solutions in New Zealand, said that to “conserve battery during the one year deployment, the solar-powered buoy samples the waves for just 20 minutes every three hours then sends the data via a satellite link. During that 20 minute recording period, the height, period and direction of every wave is measured and statistics are calculated. It’s very probable that larger waves occurred while the buoy was not recording.”

Durrant says waves may have actually reached 82 feet if the forecasts were correct.

Last week’s wave was large, but it wasn’t a world record. The World Meteorological Organization doesn’t measure maximum wave height, or, the largest individual wave. It measures significant wave height, which is meant to represent general ocean conditions and measures the average of the waves. The WMO certified a world record for significant wave height in the North Atlantic in 2013. The significant wave height was 62 feet.

The Southern Ocean makes up 22 percent of the world’s oceans, but because of the brutal environment it is the least studied and explored. Given its size, it’s likely that the world’s largest waves occur there very often, but there’s no way to measure them directly.