Crews from Humberside Fire & Rescue Service were called to the dock on Saturday evening at around 10pm and were on the scene five minutes later.
Two water rescue officers entered the water with an inflatable raft and brought the man to safety. He was left with ambulance paramedics who had been sent to the incident.
The service said the man had allegedly entered the water for a £100 bet, adding that, instead, "he was gambling with his life" with cold water known to cause shock within minutes and lead to even the strongest of swimmers drowning.
Crews train at Princes Quay regularly throughout the year to be ready for such a situation and, unlike those who enter the water, they are only too well aware of the lack of exit points around the old dock.
The incident follows warnings from multiple authorities, police forces and rescue services in the region after two children died in two separate incidents in open water in Yorkshire within days of one another in the past fortnight.
Samuel Haycock and Tomi Solomon, aged 16 and 13, died after entering the Ulley Reservoir near Rotherham and River Calder at Brighouse on Friday, May 28 and Tuesday last week, respectively.
Authorities have urged the public not to gamble with their safety by entering rivers, reservoirs, canals and other types of open water.
In the UK statistics show that Saturday nights have a higher number of drownings than any other night of the week, while such tragic incidents rise during the summer months and during spells of warmer weather.
A spokesman for Humberside Fire said: "Thankfully this irresponsible act did not add to that grim figure."
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