Ian Walters shot video of what he thinks was a great white shark about 13 or 14 feet long following them out on the water.
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"We watched it kind of go back around and start following me," said Walter. "And we just tried to keep each other calm and not give any reason for a reaction from the shark, and just led it toward some seals and eventually it let us go."
Walters told ABC7 the shark didn't do anything threatening -- it just seemed curious.
He says all he heard was a gentle bubbling under the calm waters.
Ever the science teacher, Walters told us it was a "magical moment" that's left him with a feeling of wonder.
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