Measuring 5ft 7in (1.7m) wide, the 1910 oil on canvas was offered for the first time in 40 years by dealers Brian Ashbee and Wes Wotruba. It sold to a private collector from Dorset.
The 1082-ton, 46-gun frigate depicted became famous in 1848 when Captain Peter McQuhae, his officers and his men spotted a six-foot serpent creature off the Cape of Good Hope.
“[The creature] passed rapidly, but so close under our lee quarter that had it been a man of my acquaintance I should have easily have recognised his features with the naked eye,” the captain said. According to seven members of the crew it remained in view for around 20 minutes.
It was widely reported and debated in the papers of the day, and later scientists have suggested that the ‘lizard-like’ creature was a sei baleen whale.
In 1860 it arrived in Bristol after fighting pirates in the East Indies and became a well-known feature of the docks until it was broken up in 1920.
Parsons frequently painted views of Bristol where he lived and was one of the celebrated Bristol Savages group, which was founded in 1894 and has also included painter William Titcomb and sculptor Frank Dobson.