Interesting theories from you Phil d'Conch linking US locations, however when the song was written by G.W.Hunt and performed by George Leybourne in 1872, it referenced Billingsgate, the Fish Market in the City of London (UK) - now re-located from its original location. Like wise, Pimlico is an area of London some distance up-river (River Thames) from Billingsgate. Traveling there by boat, there is a notorious bend at one point, where the wind can suddenly increase causing very choppy waters. This is no doubt the point at which the boat 'wibble wobbled' and the Bold Fisherman fell 'slick overboard.' (Hunt's lyric.)
The version used by Bogard is surely that of Hunt and Leybourne's 1872 lyric and melody, it being only slightly different - something that can happen to accommodate a particular artiste's style. Also Music Hall songs generally had variations when they were pirated from the UK into the USA in the 1800's.
The totally different lyric and melody sung by Harry Cox would date back to an even earlier Broadsheet Ballad version, which had had the same title.
Further discussion on this point will be in the shortly forthcoming Vol II of my biography of George Leybourne, 'The Heaviest of Swells.'
Heaviest of Swells