It happens rarely in Monterey Bay — perhaps a handful of times a decade at most.

Normally, the killer whales that frequent the area are familiar to marine biologists and others who track them.

So when a killer whale she didn’t recognize surfaced just 100 feet from a whale watching boat this past week, Nancy Black, a marine biologist and owner of Monterey Bay Whale Watch, was surprised.

The whale was accompanied by seven others that Ms. Black had never seen in the 30 years she has worked in the bay area.

“They were very active and social, exuberant and breaching,” Ms. Black said. “They kind of poked their head out of the water, curious of the boat. It was exciting for everyone on the boat to see.”