Two divers who were underwater off the coast of New Zealand found themselves face to face with a rare and mysterious sea creature.

Steve Hathaway and Andrew Buttle were in the waters near White Island in October when they discovered what appeared to be a 26-foot-long gelatinous worm. It turned out to be made up of hundreds of thousands of smaller organisms. They managed to capture the creature on camera as it moved slowly through the water, changing into different shapes and sizes.

The creature was identified as a pyrosome – a colony of tiny sea animals that come together to form a free-floating mass. According to the Washington Post, they were dubbed “bizarre unicorns of the sea” by scientists because of their bioluminescent glow and mysterious characteristics.

“I’ve always wanted to see one,” Hathaway told the Post. “I was beyond excited. This is like finding something that you’ve dreamed of for so many years.” Even though pyrosomes are not very rare, they are spotted only by people who spend a lot of time underwater.