Roughly 9.8 feet.
I had to cheat and use a calculator.
I surfed till my late 30’s, looking for choice breaks up and down SoCal. I was sitting outside one morning off of Sunset when I saw “something” dark at about 10 feet long pass just under my board. Figuring myself lucky to have made it back to the beach, I decided then and there to sacrifice my surfing “career”.