The 2005 photo entered into evidence shows businessman Tony Accurso scrubbing the back of Jean Lavallee, a former head of the construction wing of Quebec's biggest labour federation.
Lavallee has a cigar in his mouth with what appears to be soap on his back, arm and shoulder as the pair stand in waist-deep water.
The photo was shown as Lavallee spent his second day on the stand at the inquiry, which is looking at corruption and organized crime involvement in construction contracts, organized labour and political party financing.
Accurso has yet to appear before the inquiry, but is facing criminal charges including fraud and influence-peddling.
In recent months, the inquiry has taken an in-depth look at how organized crime infiltrated the Quebec Federation of Labour through its construction wing
Lavallee sat on the board of the federation's billion-dollar investment fund and is alleged to have tremendous sway at its real-estate investment arm. The fund was instrumental in financing numerous Accurso-led projects.
Lavallee called Accurso a friend of more than three decades.
He admitted he took about a half-dozen week-long, all-expenses-paid trips aboard Accurso's yacht, "Touch," but denied the trips were in exchange for granting contracts.
"I didn't think it was a sin to go on a friend's boat," Lavallee said.
The photo was snapped in February 2005 in the Virgin Islands on a celebratory trip after a successful contract.
When asked by commissioner Renaud Lachance if he felt uncomfortable going on the luxury boat, Lavallee shrugged it off, saying it was a common practice at one time.
Lavallee, 73, returns to the stand on Tuesday.