In Spider-Man: Far From Home, Mysterio fooled the world into thinking Earth was being invaded by interdimensional "Elementals." They were, of course, just illusions, but also fun new takes on classic comic book villains like Hydro-Man and Molten Man,
In the case of the former, there was an Easter Egg in the sequel which pointed to the real Morris Bench existing in the Marvel Cinematic Universe, but the version Spidey fought in Venice, Italy, was just a massive water creature. However, in some concept art shared by Jerad S. Marantz, we see an early take which was clearly meant to be the Hydro-Man from the comic books.
The artist explains that, "This was in the brainstorming phase. Trying to figure out what kind of [Hydro-Man] we were going to have. This was the science experiment gone wrong scenario."
Ultimately, Spider-Man: Far From Home went in a vastly different direction, but this would have been cool to see. It seems unlikely that the "real" versions of these villains would show up in Spider-Man 3, though it is feasible Sony Pictures could end up using them in one of their SUMC spinoffs.
Check out the artwork in the Instagram post below: