Fossil hunter Alex Lundberg said they first encountered the tooth, which is about 1.2 meters long, when they dived in April.
Explaining that he and his friend went back to the area and started cleaning the sand where the tooth was, Lundberg said, "The fossil started to get bigger and bigger. I remember saying to myself, 'This is a really big tooth'."
Lundberg stated that they dug the fossil from a depth of 25 meters off the coastal city of Venice in the state of Florida.
Lundberg stated that officials from the Florida Museum of Natural History will come and examine the fossil, and only then it will be possible to understand how old the tooth is.
On the other hand, Rachel Narducci, one of the museum officials, said that sometimes the fossil is allowed to remain with the finder after examinations.
"A VERY COOL PİECE"
The diver, who studied biology at the University of South Florida, said he wanted to keep the fossil in his home, "You don't know exactly where it came from.
Mastodons, the ancient relatives of modern elephants, appeared 27 to 30 million years ago and became extinct about 10,000 years ago.
They lived in forests around the world, mainly in North and Central America, and reached 2.5 to 3 meters in length and weighed up to 5.4 tons.