Mark Freeley, of East Setauket, was walking with his dog Storm when the pooch noticed something in the water in Port Jefferson Harbor.
That's when he said Storm spotted the deer, jumped into the water, grabbed the fawn by the neck and pulled it to shore.
"He started nudging it with his nose and started pulling it to make sure she was gonna be OK", Freeley said.
The video captured the weakened deer begin to run away after being brought to shore but collapsed as Storm followed it.
But the ordeal wasn't over yet.
"This time it went out even further", Freeley said.More news: American doctor agrees to travel to the United Kingdom to examine Charlie Gard
Freeley immediately called the Strong Island Animal Rescue League who arrived on the scene to assist with the ill animal.
The vet took the fawn to her vehicle, and the animal is being treated.
"I don't think I could've done it without the help of my partner".
Kutzing carried the fawn back to the rescue van.
When the animal was taken to a vet to get checked out it was found to be covered in ticks and had an eye injury.
The fawn is rescued at an area animal rescue until it can get back on its feet.