Humpback whales may be trying to communicate with us, using bubbles.

For the first time, scientists from the SETI Institute and UC Davis have documented humpback whales blowing large “vortex bubble rings” that resemble “smoke” rings during calm, voluntary interactions with humans — behavior that appears unrelated to feeding, mating or defense.

“Humpback whales often exhibit inquisitive, friendly behavior towards boats and human swimmers,” said Jodi Frediani, a marine wildlife photographer and UC Davis affiliate, in a press release.

The team observed 12 separate bubble ring episodes involving 11 whales and 39 rings across the Pacific and Atlantic Oceans. Researchers say the bubble rings differ from other whale behaviors involving bubbles.

While humpbacks commonly use bubble nets to trap prey and bubble trails during mating, these bubble rings seemed to occur only during relaxed, voluntary encounters with humans — not while hunting or competing for mates.