A 25-foot-long minke whale was washed up on Shankill beach in south Dublin during rough seas this week.
Gary Paul from Cherrywood, Co Dublin saw the whale yesterday morning on the beach. He said it was "moving around" but it was too far out for them to be able to do anything.
"It was kind of interesting to see. It's not something I've seen before and it's very unusual," he told the Herald. "I've never seen something of that size washed up before."
It was later washed back out to sea.
Minke whales sometimes wash up on the south coast, but are rarely spotted on the east coast.
The Irish Whale and Dolphin Group (IWDG) became aware of the whale on Thursday, when photos were sent to them.
Padraig Whooley, sightings officer with the organisation, said that they know the whale was already dead because it was lying belly up.
The reason it seemed to be "moving around" was because it was partially still in the sea.
"Based on images we've seen yesterday this looks most likely to be a minke whale, which are Ireland's smallest and most frequently-observed baleen whales," Mr Whooley said.
"If the numbers of whales are increasing - which we think they probably are in Irish waters - you are going to have more and more of that population washing up dead on our beaches," Mr Whooley said.
The surprise appearance comes as the IWDG prepares for its annual whale watch, which takes place next Saturday.