A tourist boat sunk in Fort Kochi on Wednesday afternoon after it collided with a fishing boat.
Eight people have reportedly died in the incident.
Police supervising the rescue operations said the passenger motor boat was carrying over 30 passengers who were going to Vypeen island from Fort Kochi.
According to a witness, the fishing boat was reversing when it hit the passenger boat.
"The accident took place about 100 metres from the Fort Kochi boat jetty, which is the international shipping route. Hence, even if someone is a swimmer, it's difficult to survive," said Samson, the witness.
"The place is frequently dredged and hence the place where the accident took place is very deep," Samson added.
Reports say that the impact of the collision was so severe that the tourist boat split into two and sunk.
Police said as soon as the accident occurred, the navy and the Coast Guard swung into action and rescued around 20 people even as the boat was sinking.
Some of those rescued died after being taken to a nearby hospital. Most passengers were residents of Vypeen.
With inputs from IANS