"Many of the tourists got trapped under the overturned boat and died of suffocation", said one of them.
Fifteen people were rescued by local fishermen.
According to reports, the boat, which had 38 people on board, overturned when trying to manoeuvre towards Pavitra Sangamam after leaving the ferry.
Addressing the media, the police said that rescue operations were on by the Vijayawada City Police and the National Disaster Rescue Force.
The incident occurred when the boat set off for Pavitra Sangamam at Ferry village near Vijayawada from Bhavani Island, the police said. Sixteen people have drowned in the incident. The driver of the boat agreed to take them to Pavithra Sangamam at a cost of Rs 300 per head. Of them, 32 belonged to a walkers' association from Ongole in Prakasam district and six from Nellore.More news: After NGT rap, Delhi government defers odd-even
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According to the AP State Disaster Management Authority, there are two NDRF teams with 30 members each, 45 members of the State Disaster Rescue Force and 12 rescue boats now working on the rescue operation. Home minister N Chinna Rajappa announced at 8.30 pm that 16 dead bodies were retrieved till now.
A total of 15 people were rescued with the help of locals.
Two persons, who were rescued from the tragedy, complained of sickness and were shifted to a government general hospital in Vijayawada, the officials said.
Andhra Pradesh Chief Minister N Chandrababu Naidu has condoled the loss of lives in the mishap.