It's not clear what caused a deep gash down Eugene Finney's back while swimming in the ocean with his daughter, but it's clear the brush with danger helped save his life.
Finney, from Fitchburg, Mass., was visiting his parents in California in July with his two kids and girlfriend.
While swimming about 100 yards off shore in water about 10- to 15-feet deep, Finney said he turned and saw a large wave approaching and quickly grabbed his to dive under the breaking wave.
When he tried to surface, he was hit by a large object.
"I was hit in the back hard. Really hard. I've never been hit that hard in my life," Finney told CNN.
When he came up bleeding and went for medical treatment, he learned there was a more serious health issue at hand.