"She's effectively had to face this alone," Judge Robinson said.
Goatley had been drinking with friends and their revelry led them into the city's student quarter where several house parties were taking place.
Uninvited, the defendant entered the home where up to 50 people were drinking.
When partygoers started drifting away in the early hours, Goatley ventured into a bedroom where a woman was sleeping.
Despite not knowing the victim, he removed his jeans and shoes, climbed over her and lay down.
Later, Goatley kissed her and, thinking he was her boyfriend, the victim made no strong objections.
The defendant went on to rub her body and fondle her genitalia, stopping when she told him it was "gross".
At 4am, the woman's boyfriend returned and the reality of what had happened became clear.
Campus Watch attended and informed police who apprehended the defendant.
Counsel John Westgate said his client was "incredibly drunk" that night and had been punished for his actions from the moment he was found out.
"Boy, has he paid for it in many, many ways," he said.
"His world was turned upside down. He was humiliated, he was embarrassed, he was isolated."
The court heard Goatley drank alcohol twice a year in 2019 but when he started university in 2020 it increased drastically to twice a week.
Westgate said the defendant had sought counselling for his drinking and since been abstinent from alcohol.
Goatley wanted the victim to know he was "not a pervert or a risk to people", he said.
Psychological reports underscored that, putting him at a low risk of reoffending.
The discharge-without-conviction application was based on Goatley's future job opportunities being stymied, potential overseas travel being curtailed and the impact on his self-esteem.
The judge, however, categorised the offence as "serious" and said that could not be overcome by those possible consequences of a conviction on Goatley's life.
"This was sustained intimate contact with a person who was vulnerable in a situation where you shouldn't have been there," he said.
"A message needs to be sent that indecent sexual assault of alcohol-affected women will be responded to seriously by the courts."
Goatley was sentenced to six months' community detention, 275 hours' community work and nine months' supervision.
He was ordered to pay the victim $2000.