A Danish paramedic said McPherson's attempts at CPR were "very bad", leading prosecutors to question whether he was "really trying", the Daily Mail reported.
Days after her death, while McPherson was still in Denmark, he completed an online application to join a support group called Widowed and Young.
Prosecutor David McLachlan QC said: "His wife had been dead eight days, her body had still yet to be repatriated and laid to rest, and he was joining Widowed and Young."
McLachlan told the court that McPherson later described the group as "like Tinder for widows" in a conversation with his personal trainer.
At 1.46pm on June 6, the last day of their holiday, McPherson called emergency services.
A paramedic found McPherson giving Leeson CPR as she lay beside the pool.
The paramedic said McPherson "had not pressed hard enough", and had "apologised because he had an injured shoulder".
McLachlan said: "He thought that Donald McPherson's resuscitation attempts to supposedly save his wife's life were very bad, as there was still so much water inside her lungs" and asked the jurors to question whether McPherson "was really trying", the Daily Mail reported.
The morning after Leeson's death, McPherson shifted funds from their joint accounts to accounts under his own name.
Prosecutors say made the transfers to reduce his credit card debt.
Initial investigations from Danish authorities determined that the death was "assumed accidental".
McLachlan said: "The prosecution case is that her death was far from accidental".
Leeson's mother Betty Leeson also read a statement to the court in which she said it was "strange" that McPherson did not visit his wife's grave for months after her funeral or show emotion at her funeral, the Press Association reported.
Betty Leeson added: "I know he is seeing someone else. Paula was only buried in July. He was seeing an Asian lady by October."
The deceased's brother Neville Leeson told the jury McPherson was "reluctant" to hand over Leeson's iPhone after her death.
When the family eventually got the phone they found selfies of the smiling couple taken on the day she died, despite McPherson telling police that they had been in bed and when he got up he found her lifeless body in the pool.
The court previously heard that McPherson, originally from Auckland, was keeping secrets from Leeson, whom he married in 2014 in a lavish ceremony at a historic British castle.
McLachlan told the jury that the "big secret" was the insurance policies, but also told them that forensic handwriting experts would prove that McPherson forged her will to make himself the beneficiary.
By 2016, McPherson was paying nearly $900 a month in premiums for the life insurance policies. Prosecutors said he never missed a payment despite heavy debts.
McLachlan also told the jury that McPherson, who grew up in Auckland with his parents and two sisters, told his wife that he was an orphan to avoid discussing his past.
He had also trained to be a pilot, keeping his training secret from Leeson by claiming to be working if she called during his flying lessons.
The trial continues.
