Reema Sondhi, 42, her 23-year-old nephew Jagjeet Singh Anand, 20-year-old niece Kirti Bedi, and 20-year-old family friend Suhani Anand all died at Victoria's Forrest Caves Beach on January 24.
They were visiting Phillip Island for a family day trip and were part of a group of nine with relatives from India.
But Mrs Sondhi, Mr Singh Anand and Ms Bedi would never make it home as they were pulled unconscious from the water and died on the beach. Ms Anand died in hospital the next day.
Kane Treloar said the victims had limited or no swimming ability. (Rachael Ward/AAP PHOTOS)
Coroner Sarah Gebert found all four had drowned after being caught in a rip, in findings released on Thursday.
Aerial footage from the incident and photos of the beach showed a single primary rip that was in effect at the time of the tragedy, Detective Senior Constable Kane Treloar submitted to the inquest.
Forrest Caves Beach, one hour and 45 minutes from Melbourne, is a southwest-facing beach which is highly exposed to high-energy swells that come from Bass Strait.
Beaches along the southern side of Phillip Island are known for their strong rips.
The victims all had limited or no swimming ability, nor knowledge of Australian beaches, Det Sen Const Treloar said.
"Only an experienced swimmer with experience and understanding of rips would have been able to extricate themselves," he said.
Signs at the beach's entrance had general warnings including, "No Lifesaving Service", "Dangerous Currents", and "Submerged Objects" and were clearly displayed and visible on the day, lead investigator Sergeant Leigh Cole said.
But he noted there were no provisions to translate the messages into foreign languages.
Other group members later told police that they did not notice any warning signs.
Sgt Cole's investigation concluded the group's failure to notice warning signs and lack of swimming ability to identify rips or how to escape one led to their deaths.
Ms Gebert said education, safety and water awareness "is paramount" to prevent more fatal drownings this summer.
"It appears that in many cases, including this coronial investigation, clear signage warning of risks alone is inadequate," she said.
"I implore the Victorian community and visitors to our state to be aware of the risks of Australian beaches and take precaution where needed."
The deaths were the state's worst beach tragedy since 2005, when five people drowned at Stingray Bay near Warrnambool, according to Lifesaving Victoria.
