Who is John L. Bigalow from Raise the Titanic! and what is their importance?

Bigalow was a crew member on the sinking ship. As the ship was sinking, a passenger forced him at gunpoint to lead him to the ships vault. The passenger, claiming to have killed eight men, locked himself in the vault and went down with the ship. Bigalow made it to the top and was dragged into a lifeboat and rescued. He spent the next seventy-six years wondering about the passenger and the men that he claims to have killed.