Thai police say they are treating the death of a British backpacker at the resort island of Koh Samui as murder.
A post-mortem examination on Katherine Horton, 21, from Cardiff, found she was attacked with a blunt instrument and then left to drown in the sea.
The Reading University student was last seen just hours before on New Year's Day as she spoke to her family on her mobile phone on a beach.
Her family said she had warmth, vivacity and a passion for life.
South Wales Police said they were liaising with Thai police and had been awaiting confirmation from them that Miss Horton was murdered before deciding whether to send officers to Thailand.
A forensic scientist said her clothing was dishevelled; she had head and other internal injuries and bruising on the arms.
Miss Horton, who was due to return home next week after a couple of weeks in Thailand, was with friends on Lamai beach on the evening of 1 January.
She is reported to have wandered away from them as she spoke to her mother on her mobile phone. What happened to her between that moment and the discovery of her body is unknown.
The student had arrived on the island on New Year's Eve
A Foreign Office spokesman said her body was found by a water biker at 10am local time on Monday.
Major Thanongsak Aksornsom, chief investigator on Samui island, said Miss Horton had been dead "for less than 12 hours".
"It's unlikely that this case was an accident but so far we have not issued an arrest warrant and are not interrogating any suspects," he added.
Dr Pattana Kitkailart, who carried out a post-mortem examination, said: "There were wounds on her head from being hit with a blunt object and on her body and arms there were signs that she was dragged."
On Tuesday, Miss Horton's father left the family home in the Thornhill area of Cardiff for Thailand, while her brother was travelling there from his home in Australia.
A statement from the family - parents Elizabeth and Ian, and older brothers, Richard and Christopher - read: "Katherine was much loved by all her family and friends. We will miss her warmth, her vivacity and her passion for life.
"She brought us so much happiness and words cannot express the emptiness we feel at our loss."
Her former head teacher, Robert Smyth of Llanishen High School, said: "Katherine was an outstanding student in every respect, popular with her peers, and extremely well remembered by all staff who came across her."
South Wales Police Detective Superintendent Paul Kemp said: "Thai police are very experienced and very capable of dealing with this sort of incident. But we will liaise closely.
"We have a responsibility in the UK, if a citizen of the UK dies as a result of murder, obviously we have responsibility through the coroner to inquire into the circumstances."