Captain Widdershins (Introduced in: "The Grim Grotto") is the captain of the Queequeg, his submarine. He is the stepfather of Fiona and Fernald.
In The Grim Grotto, he finds Violet, Klaus, and Sunny Baudelaire at sea while he is looking for the sugar bowl and takes them aboard the Queequeg. He is extremely emphatic, with almost all of his sentences being exclamations, and permeates his speech with the word "Aye!" His personal philosophy is "He who hesitates is lost", which the Baudelaires find to be unreasonable. Captain Widdershins is considered the eleventh guardian of the Baudelaires. He seems aware that Fiona takes a fancy to Klaus (he accuses them of flirting when Fiona is surprised that Klaus knows what a mycologist is), stating that if Klaus finds the sugar bowl, he will "allow [Klaus] to marry Fiona."
After sending the Baudelaires and Fiona into the Gorgonian Grotto, he and Phil appear to desert the Queequeg. The reason may have to do with a woman who approached the Queequeg to tell Captain Widdershins something involving him being required to leave the submarine. In The Penultimate Peril, Kit Snicket says that she intends to meet Captain Widdershins and is later mentioned water-skiing towards and, soon after, away from him.
Kit had contacted all three of the Quagmire triplets as well as their guardian, Hector, and had met with them and the crew of the Queequeg when their self-sustaining mobile home crashed into it. This reunion was short-lived, however, as all of the crew as well as the triplets were picked up by the mysterious '?' Shape (dubbed by Kit Snicket as 'The Great Unknown'). Another note to make is that though he himself stated that The Great Unknown was "something worse than Olaf himself", he seemed to insist to take his chances with it, as mentioned by Kit Snicket in The End. It is possible that Captain Widdershins also has, or had, a fortune because when Count Olaf is talking about all the fortunes he will obtain, he says "the Widdershins fortune".
In The Grim Grotto, Widdershins says that Fiona's mother died in a manatee accident, although Fiona hints that he wasn't telling the truth about her mother's death.