Herbert Dawes was a member of the crew of the Karaboudjan.
He made contact with a Japanese policeman, Bunji Kuraki, and intended to denounce the unlawful activities of the ship and its crew. He had just enough time to write a track on a piece of paper before he was discovered and murdered by his crew mates, led by first-Mate Allan Thompson. He was the key to the story in The Crab with the Golden Claws, since the discovery of his body was what started the investigation of the case by Belgian authorities, and the piece of paper, later found by Tintin, was what helped them discover the people involved in the plot.
In The Crab with the Golden Claws, his body is found by the police and referred as a "drunken man" while his full name is not revealed until Kuraki is freed. In The Crab with the Golden Claws tv episode, his full name was stated, but he is still referred as "drowned man." The episode also portrays Dawes's meeting with Kuraki, and his murder, both of which were only mentioned in the book.