By Selena Hill (staff@latinospost.com) | First Posted: Aug 05, 2013 06:35 PM EDT

"I still can't believe that it happened. I'm finding it hard to believe," said Evonne Cashman to KHON2 after surviving a shark attack off the Hawaiian island of Maui.

The 56-year-old retired teacher was snorkeling alone about 30 feet off of Ulua Beach in Wailea last Wednesday when she encountered the massive shark. It slammed into the California woman at 8:45 a.m. while she was in about 10 feet of water. Cashman says the water was murky and she didn't see the shark approach her.

"It happened so fast. I didn't see him coming. I didn't see it going," Cashman said, according to Fox News affiliate KDRV.

"I must have had my hands up in front of my face. I think my head was above water, if I remember correctly. I don't know because it happened so fast. I didn't see him coming. I didn't see him leave. He just came and hit me hard and bit me hard and I just took off to the shore as fast as I could," Cashman told KHON2.

"I got hit really hard and bit and then he let go as quickly as he bit me. And then I just started swimming to shore as fast I as I could, yelling 'help' the whole way," Cashman said.

After the attack, Cashman was rushed to the Maui Memorial Medical Center where she underwent emergency surgery.

The bite left a 15-inch wound from running from the middle of her spine to her neck. She also suffered injuries to her chin and both hands.

Based on her injuries, doctors believe the shark was huge.

"He thinks according to the bites and where they are and what they look like, it was probably about a 25-foot shark. That was his guess," Cashman said.

Maui County and the state immediately closed off the area a mile in both directions. Signs were also posted warning people not to enter the ocean.

"He only bit once and he let go right away thank goodness and I'm grateful to God for that," Cashman said. "My mask was gone. I think that might have been what protected my face from getting more."

Watch video of Cashman after the attack below:

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