Three Burmese men jumped into a lagoon in Koh Kaew in Phuket on Wednesday night trying to rescue a monkey but one drowned.
Kusoldarm rescue divers were notified that a man had drowned at about 6pm.
Mae Au, 38, was waiting near the lagoon to tell rescue divers that his 18-year-old son, Set Pai So, had drowned.
Rescue divers took 15 minutes to find the body in the lagoon and it was taken to Vachira Phuket Hospital.
Mae Au told rescuers: “At about 5pm we were working near the lagoon. My son saw a monkey that fell down into the lagoon and was trying to swimming back to land.
“My son and his two friends jumped into the lagoon. One, who is a good swimmer, grabbed the monkey and pulled it back to land.
“My son and the other friend were slowly swimming after him. But my son was getting tired. His friend was trying to help him but failed.
“I was standing watching my son drown and I couldn’t help him.”
The police said they took the men to Phuket City police station to question and console them.