It was a pair of mother-calf blue whales, N Vasudevan, Chief Conservator of Forest (Mangrove Cell) told PTI.
This is the first time in over 100 years that whales have been spotted along Maharashtra coast, he said.
The last such spotting recorded was in 1914, Vasudevan said.
The whales were spotted recently by a group of researchers, 3 kms from the Sindhudurg coast between March and May. The researchers also spotted four Bryde's whales during the period.
Under the UNDP project, the Cetacean Population Study team also sighted 687 dolphins, of which 153 individual dolphins were identified because of distinct features such as their fins.