A pod of around 50 dolphins was spotted off the west coast of Cork on Sunday evening.
The bottlenose dolphins were sighted in Baltimore Harbour by journalist Flor MacCarthy who posted the below video to Twitter.
The video has already been viewed more than 33,000 times.
Ms MacCarthy told thethat her husband and son spotted the pod of bottlenoses while they were out on the water, and shortly after she joined them they were "surrounded".
"Word spread and there were about ten boats eventually, mostly families with kids," she said.
"Some were sailing, those with engines turned them off or put into neutral and we drifted with dolphins.
"It looked like an end-of-summer spectacle that they had been choreographing for weeks."
Ms MacCarthy says they were "mesmerised" by the synchronisation of the dolphins.
"Had to keep a tight hold on our dog Luna as she wanted to swim with them."
She added: "We’re on the water here all summer between Baltimore and the islands of Sherkin, Heir Island, Cape Clear and Horse Island and we see dolphins here often.
"This is the first time we’ve ever seen them in such numbers within Baltimore Harbour."