Fifteen people, all small traders from Chembur suburb in Mumbai, hired a mini-bus and went to the beach for a picnic, an official at Murud police station told PTI.
While they were enjoying the picnic, six of them ventured into the waters for swimming and drowned, he said.
The other picnickers immediately raised an alarm and informed the police.
After a few hours, owing to high tide, the body of one of the six was found floating near the beach.
Later, by the time police reached the beach-side at around 2 pm, five more bodies were found floating in the waters, he said.
The bodies were brought to Murud government hospital for post mortem, the official said.
The deceased have been identified as Rohit Jhala, Vinod Zalai, Sanjay Panchal, Dinesh Pawar, Dilip Gole and Shankar Chavan (all in the age group of 40-45 years), he said.
A case has been registered in this regard, he added.