Several party-goers approached Grant Kennedy, the host company's group operations manager, to discuss Mr Grace's behaviour.
He confronted Mr Grace on the top deck and an argument ensued, which escalated into a physical struggle.
Another employee, Sean Robinson, intervened and tried to get Mr Grace back into his seat.
Mr Grace was described as "going completely bananas... flailing around'' and Mr Robinson restrained him until he calmed down.
When he let him go he got up again and punched Mr Kennedy in the nose.
Mr Robinson restrained him again, forcing him onto a couch and using his bodyweight to stop him breaking free, while Mr Grace kicked his legs around and cursed.
"Mr Robinson states there was a significant amount of physical exertion required to restrain Mr Grace, and he was employing whatever means he could to prevent Mr Grace getting up and resuming his aggressive behaviour,'' the coroner said.
At one point during the struggle Mr Robinson's left shoulder would have been to the right side of Mr Grace's neck.
He eventually stopped struggling but Mr Mr Robinson feared he might just be "playing possum'' and that he would continue fighting as soon as he let go.
When Mr Robinson released his grip, he was unresponsive and CPR could not revive him.
The coroner formed the view that the actions of Mr Robinson were reasonable in the circumstances and that he had acted in a controlled manner, despite "significant provocation'' from Mr Grace.
"I am also satisfied that the pressure applied to Mr Grace's neck during the struggle was accidental and without any intent on Mr Robinson's part to cause Mr Grace harm.''
Mr Grace also had multiple rib fractures, however, there was insufficient evidence to establish whether these had been caused during the struggle or were a result of the vigorous resuscitation attempts, the coroner said.
A post mortem revealed Mr Grace was having a heart attack during the struggle, which began at least seven hours prior to his death. This would not have killed him but it would have affected his ability to withstand the stress of being restrained.
Analysis of Mr Grace's hair indicated he had used methamphetamine some point in the three months of his life and an ESR reports stated he had 229 milligrams of alcohol per 100 millilitres of blood when he died, nearly three times the legal alcohol limit for driving.
Police initially treated the death as homicide after it was revealed Mr Grace was asphyxiated.
