Swimmers set to dive into the San Francisco Bay for an Escape From Alcatraz triathlon are on alert after new video shows a white shark attacking a seal in the area.
Video by a security camera on board an Alcatraz Cruises ferry captures the shark shooting out of the water with a seal in its mouth.
"I knew what I was seeing," said Chase Corum, a port captain for Alcatraz Cruises. "I couldn't believe what I was seeing."
Corum was in the pilot house of the boat when he saw the shark.
"I saw red in the water, saw blood in the water and a shark thrashing around," Corum said.
Meanwhile, aquatic park members at the Dolphin Club are training for the 35th Escape From Alcatraz triathlon. Organizers said 59 swimmers are signed up to jump in the water near the scene of the shark attack.
"The chatter is it's going to be interesting Saturday morning," said David Haskel of the Dolphin Club. "People here have some nerves going in the water. That was a big pool of blood right by Alcatraz."
A sign at the club said they are monitoring the situation.
New video of a white shark attacking a seal near Alcatraz is giving swimmers something
Stephanie Jung, an education specialist at the Aquarium of the Bay, said the video is important for researchers. It is believed to be the first white shark attack in the Bay caught on camera.
"It's fantastic showing what the Bay has in terms of animal life here," Jung said.
Jung added research shows the incident is not the first time a white shark has been in the Bay and it will not be the last.
"From tagging and tracking they do come into the Bay, more likely preying on seals and sea lions," Jung said.
Swimmers competing in the triathlon are set to practice Friday morning. The race will take place on June 12.