Others were rescued, said Praful Patel, the administrator of the Union Territory.
All the tourists were from Maharashtra and were visiting a resort in Khanvel town.
The lake is situated outside the town.
Patel said the boat had been newly purchased by the resort owner, and he had invited his relatives and friends from Mumbai and other places in Maharashtra for its first ride when the mishap took place.
Rescued persons were taken to a hospital in Silvassa.