A porpoise has been found washed up on Ballyholme beach near Bangor, County Down.
Two members of the public went in to the water to try and help the mammal on Tuesday evening.
Bangor Coastguard Rescue Team members who were training in the area, were called to the scene by police at 19:42 BST. They got the two people "out of the water and to a place of safety".
The Coastguard said the porpoise had died.
The Northern Ireland Environment Agency was contacted to assist with the removal of the animal.
Ross Gray, senior maritime operations officer for HM Coastguard, has urged people not to enter the water to rescue animals.
'It's understandably distressing to see an animal in difficulty in the water, but we would urge people not to attempt to enter the water to try to rescue it, you could easily get into difficulty yourself," he said.
"If you see a stranded animal on the beach call 999 and ask for the Coastguard."
It was initially thought that the mammal was a dolphin, but it was later confirmed to be a porpoise.
Porpoise or dolphin
- Dolphins usually have bigger mouths and more curved dorsal fins
- Porpoises are generally smaller than dolphins and lack the distinctive beak
- Dolphins are more prevalent than porpoises
- Dolphins are more talkative than porpoises
- Both have many similarities, including extreme intelligence