Conservationists have confirmed what they believe is the first sighting of a humpback whale in Cardigan Bay.
Humpbacks can live for up to 77 years
Up to three adults were spotted 100 metres off shore at Ynys Lochtyn, near Llangrannog, Ceredigion.
An expert said it was unclear why the mammals, which can weigh up to 30 tonnes, had strayed into the bay.
During the summer they are more commonly found off south west Ireland and north west Scotland.
The humpback sighting was confirmed by the Sea Watch Foundation's Hanna Nuuttila. She said they were spotted by a fishing and a whale and dolphin pleasure boat on 16 July.
Miss Nuuttila, from New Quay, added: "To see humpback whales in Cardigan Bay is very, very unusual.
"A person on the boat saw what she assumed were humpback whales, but she didn't want to say anything because it would have sounded so ridiculous.
CARDIGAN BAY FACTS
There are believed to be 140 resident bottlenose dolphins in the bay
They are seen from New Quay to Aberystwyth
Humpback whales can weigh up to 30 tonnes and can live for 77 years
Humpbacks are renowned for their extraordinary and complex songs
They can measure up to 15m
"But someone suggested that they were humpbacks and then photographs were taken and that's how we identified them.
"We believe it's the first ever sighting of humpback whales in Cardigan Bay".
Miss Nuuttila, Sea Watch Foundation's sighting officer, said it was unclear why three humpback whales had drifted into the bay.
"I don't know if the sighting is linked to warm seas or increasing whale numbers", she said.
"This is big news and very interesting and if it happens more frequently and a trend is set then we'll be able to say more conclusively why humpbacks use Cardigan Bay.
"They would have been travelling through".
Miss Nuuttila added that changing sea temperatures were attracting more species like the striped dolphin, usually found in the Mediterranean, further north.
The foundation's national whale and dolphin watch week starts on Saturday and it is hoping for a record number of sightings of marine mammals this year.
The study takes place every year, giving members of the public a chance to learn more about the 28 species of whales, dolphins and porpoises found in UK waters.
Holidaymakers, walkers, fishermen and bird-watchers are among those who are asked to send in their sightings of marine mammals.
Their reports help experts research the mammals' behaviour.