Flint Marko, a.k.a the Sandman or the Hydro-Man, is a villain in The Legend of Spider-Boy. He is an average high school bully until he ends up getting super-powers.
In the first episode of Legend of Spider-Boy, Peter Parker is framed for a prank by Flint, who has been bullying him for years. Later on, Flint tries to fight Peter, but Peter all of the sudden overpowers him and beats him.
The next day, Flint shows up to first period (Mrs. Osborn's class) early for a change. He notice Ms. Osborn isn't in the classroom, and he looks at the contents of her desk. He notices a weird plastic bin with a sheet over the top. Flint opens the bin and there is green, glowing sand inside. Flint grabs some, and puts it in his pocket.
Afterwards, in the middle of class, Flint begins feeling strange. Another student looks at his shoes and freaks out, as tons and tons of sand is leaking out of it each second, with the sand nearly covering the entire classroom floor. Flint lets out a deep moan, and he dissolves into a pile of sand. Everyone freaks out.
Suddenly, the sand begins moving, like it's alive. It turns out Flint is still alive, but he's made entirely out of sand. He begins destroying everything. Peter runs out of the classroom, but realizes he must do something about it. Peter goes to the lost and found, where he finds a red mask. Peter takes it and puts it on, then uses his powers to fight the rampaging Flint.
Peter ends up defeating Flint by shooting a web at the sprinklers above them and pulling it off, shooting water all over Flint and turning him into a pile of mud. SHIELD scientists take away Flint to examine him. While they are operating on Flint, he comes back, but the mud is too heavy to move in so rather than using the mud to move around Flint takes all the water from the mud to transform into a Hydro-Man.
The new water Flint escapes containment and starts rampaging through the streets of Manhattan. Peter sees it on the news and puts the red mask back on so he can swing into action and save the day. After another battle, Peter manages to defeat Flint a second time, by luring him to a tall rooftop where he distracted him until he evaporated. SHIELD workers managed to suck the gaseous form of Flint into a vacuum pack, trapping him until they could turn him back into a human.
- Shape-Shifting - In his sand form, Flint Marko could change around his sand body into different shapes and sizes.
- Liquid Body - In his water form, Flint Marko was made up entirely out of liquid.
- Sand Blasts - In his sand form, Flint Marko could shoot out bursts of sand at high speeds.
- Rock Body - In his sand form, Flint Marko can harden his body into rock.
- Super Strength - In his sand form, Flint Marko can push tremendously heavy objects up with his sand grains. In his solid rock form, he can lift objects all on his own.