A Pacific Whale Foundation snorkeling vessel was visited by a rare Hawaiian monk seal while moored off Lana'i on Wednesday.

The endangered mammal climbed onto the swim steps at the stern of the Ocean Quest catamaran, according to foundation spokeswoman Anne Rillero. Crew members on the foundation's Lana'i Wild Dolphin & Snorkel Eco-Adventure kept passengers away from the monk seal, she said.

The seal was wearing a satellite tag and had tags on its hind flipper. When crew members called NOAA Fisheries' monk seal hot line to report the sighting, they learned that the 2-year-old female born on the Big Island has become desensitized to humans, Rillero said.

The seal eventually left the vessel on its own, leaving behind some fish it had caught. Photos of the encounter were not immediately available.

The seals, found exclusively in the Hawaiian Islands, are known to be aggressive toward humans and should not be approached on land or sea. Their population numbers an estimated 1,200.