Among the missing was a Down syndrome son of a Melbourne family holidaying in Phuket, Thailand.
Paul Giardina, 16, became separated from his parents, Joseph and Ivana Giardina, from the Melbourne suburb of Rosanna, when a tidal wave hit the resort centre yesterday, ABC radio reported.
Both parents were injured when the wave hit a restaurant in which they were dining, with Mr Giardina ending up on the fourth floor.
'The water just came over'
"We were at the Seaview (hotel) in Patong, in the restaurant having breakfast and everybody was really curious at what was happening," Mrs Giardina told the ABC.
"They've gone to the beach. They've crossed the road to get a closer look. We're all watching.
"When the pier started flooding across, the water was coming, everybody started running and panicking.
"The water just came over. (The restaurant) just filled up."
She said furniture was knocked around and she saw a car floating by her.
"The pier, with boats attached, just floated down the beach," she said.
"The three of us were together and I couldn't get to my son because I had furniture, the tables and chairs, from outside had gone in between us.
"My husband Joe ... was calling me and they just went."
Mr Giardina said the water hit with enormous speed and he was pinned again a wall.
"I was under water. I tried to get out. I couldn't do it," he said.
"They say they found me on the fourth floor. I have no idea how I got up there."
Mr Giardina said their son was barely able to communicate. "At best they'll get a name out of him," he said.