He's never seen one swimming free, but Mexican scientist Ramon Bonfil has sawfish on his mind every day he goes to sea looking for the DNA remains of what he describes as a "fantasy" fish, and which he longs to save from extinction.
Bonfil, now in his 50s, told EFE that from the time he was a boy he has been fascinated by these shark relatives that he would see in Mexican comics of the 1960s, when "people were still very aware of them" and took it for granted they were living creatures.
The oceanographer, founder of the civil association Oceanos Vivientes (Living Oceans) - dedicated to promoting the health of aquatic life - estimates that at present "several dozen" sawfish must survive in Mexico's shallow estuary waters and coastal lagoons.
For Bonfil, who since 2015 has been looking for something he has never seen, that's enough. His dream is to find them and someday restore their population so they are no longer threatened with extinction.
He has obtained funding both from the government - which since 2017 no longer aids him - and from foreign organizations as well as from private donors.
It's not much, but enough to lead a team "of four or five helpers." The truth is he hasn't seen "a single peso in the last three years," he said.
That complicates everything, since his assistants stick with him out of love for those big fish and have to take time off from their regular activities to do so.
On the other hand, Bonfil can keep at it full time since he lives with his father who provides him with food and shelter. That's enough for him, and the specialist in ecology, conservation and shark and ray fisheries continues his plan to find the species.
It all began with a study of the Mexican coast that lasted three years "asking fishermen and locals if they had ever caught a sawfish, if they knew about them, and when was the last time they saw one."
"The results indicated that very old fishermen were familiar with them and young ones weren't," he said.
They began to silently disappear in the 1960s and '70s, with the situation getting worse in the 1980s, when they became "very scarce."
There were sightings in the 1990s, the year 2000 and even 2010, with fewer sawfish seen all the time, "but not always with real evidence to support what the fishermen said."
While traveling the coasts speaking with fishermen, he started tossing fishing nets into chosen shoreline waters to see if he might come up with a sawfish and plant a geolocator on it. No such luck.
In 2017, by then without government funding but with some foreign capital, Bonfil chose to seek some invisible tracks and concentrated on taking DNA samples from waters where the big fish were known to have once been abundant.
"Coastal lagoons, bodies of water, sanctuaries, beaches," he said.
There he and his assistants apply a very novel technique they call "environmental DNA," which determines if there are any DNA remains of the sought-after species in a particular stretch of water.
If the DNA is found, it means the sawfish still lives, since the genetic code present in the cells does not last more than three weeks or at most a month in the water.