Whale watchers in St. Andrews, N.B., got a lot more adventure than they expected when they witnessed a shark during a whale-watching tour aboard the Jolly Breeze.

“Passengers were just watching seals laying on the rock and all of a sudden we saw fins," says Jolly Breeze crew member, Erika Head.

People on board watched as fins sliced through the surface of the water in what appeared to be a great white shark attacking the seals.

"I was really shocked,” says Head. “I wasn't expecting to see that, but it was really fascinating that I got to see that."

Senior marine biologist for Island Quest Whale Watching, Nicole Leavitt-Kennedy, says her crew caught the tail end of the attack.

"They did have a large 12-15-foot great white shark that was essentially eating a seal off of one of our seal rocks."

Leavitt-Kennedy says six main species of sharks reside in the Bay of Fundy, noting the sighting isn’t a total rarity.

"We have white sharks, basking sharks, blue sharks, porbeagles, threshers and makos,” says Leavitt-Kennedy. “I'm not going to say they're as common as you would see them every time you go out on the ocean – but they are there."

However, some people say shark sightings have increased recently.

"There was maybe a ten-year period we didn't see any great white sharks at all,” says Jolly Breeze owner, Joanne Carney.  “And the last five years we've had a few sightings – so potentially it's been on the increase."

Regardless of whether the sighting is indicative of more sharks in nearby waters, those who witnessed the shark won’t soon forget the experience.

"I'm really thankful that I saw that actually,” says Head. “I think they're pretty awesome creatures."

Meanwhile, Levitt-Kennedy says it’s not a sight those on the whale-watching excursion will likely see again.

“It’s not something that you will probably ever see again as someone visiting,” says Levitt-Kennedy. “It is probably a once in a lifetime thing."

With files from CTV Atlantic's Laura Lyall