Dale Pike, 25, of Glynneath, Neath Port Talbot, "stood and watched" as Gareth Pugh dived into the lake with a weighted belt to fish out balls.
Mr Pugh's body was found in the water at Peterstone Lakes Golf Club, near Newport, after he lost his breathing equipment and drowned in February 2016.
Pike received 32 months after admitting manslaughter by gross negligence.
Cardiff Crown Court heard Pike raised the alarm when he noticed a constant stream of bubbles rising to the lake's surface and a flotation device carrying Mr Pugh's air supply floating towards the edge.
Emergency service staff pulled him from the water 70 minutes after he first entered and he was found with his feet pointing upwards, weighed down by a weighted belt and a 16kg (35lbs) bag of 341 golf balls he had retrieved.
The court heard Pike, who ran Boss Golf Balls which sells balls retrieved from lakes, should have hired trained divers to carry out the work, at a cost of about £1,000 a day.
But instead he employed Mr Pugh, who had ADHD and learning difficulties, and paid him £20-40 a day.
David Elias QC, defending, said Pike "naively and foolishly believed that all would be well with the use of that equipment in that lake".
Sentencing Pike, Judge Keith Thomas said: "Mr Pugh was an unsuitable contender for the diving work you employed him to undertake, but you allowed him to take those risks to make a quick buck.
"The risk of death or serious injury was obvious to you, but your cavalier attitude towards safety was the cause of Mr Pugh's death.
"With hindsight you bitterly regret what happened."
Speaking after the hearing, Iwan Jenkins, from the Crown Prosecution Service, said Pike "stood by and watched" as Mr Pugh entered the water "knowing that safety regulations were being breached".
"His deceit and callousness resulted in Gareth losing his life," he said.
"There was clear evidence Pike had made enquiries with legitimate dive operators to cost this activity but he chose not to use them, instead falsely claiming to the golf club that he was a qualified commercial diver with his own equipment."
Mr Pugh's partner Mayree Worton said: "What upsets me the most is the bond that our daughter and Gareth had together is no longer there.
"The sentencing of Dale Pike is a relief, however it doesn't make what has happened any less painful, upsetting or distressing and it does not bring Gareth back."
A golf company director has been jailed after a ball collector drowned in a freezing course lake.