Horrified divers found the words 'TRUMP' carved into the body of a manatee.
The stunning animal was seen swimming off the coast of Florida with the huge letters etched into its back.
Witnesses spotted the sea creature in the Blue Hole headwaters of the Homosassa River - around 128km north west of Orlando.
The incident was reported to animal authorities who have launched an investigation to find the cruel abusers.
Writer, Yashar Ali, who shared footage of the defenseless animal on Twitter said: "Here is the video of the poor manatee that had TRUMP carved into its body.
"Minding its own business and some monster(s) came along an did this.
"f you have information on this person(s) who committed this federal crime, please call 888-404-3922."
Craig Cavanna, a senior federal wildlife officer in charge of the investigation, said: "It’s been my experience that this is very out of character for this community.
"Wildlife conservation is a core value in Citrus County. That’s why it’s called the Nature Coast."
Harassment of manatees, which are protected by the Endangered Species Act, is a Class A federal crime that carried a $US50,000 (£36,000) fine and/or up to a year in federal prison, reports the New York Post.
Mr Cavanna said his team are now desperately hunting for those responsible.
The slow-moving creatures migrate to the area along the county's western coastline every year and are easily accessible by those on boats or swimmers.
The incident came just days after the US Capitol was raided by a violent mob.
In scenes which shocked the world, hundreds of Donald Trump supporters descended on the government building in protest against Joe Biden being named President.
Congress members were inside the Senate chamber, completing the official Electoral College vote count, when rioters breached police barricades and began marauding through the Capitol.
President Trump was banned from Twitter and Facebook after it was deemed he had been inciting violence as the unrest continued.
