The actor was unhappy with a plot which saw his character Boyd Hoyland cheating on his wife Janae, played by Eliza Taylor-Cotter.
Kyal became so disillusioned with the show that he was happy when his contract was not renewed by bosses. He filmed in final scenes in April but has not yet departed on UK or Australian screens.
"I absolutely hated my character at the end. I couldn't believe what they made me do," Kyal, 19, told the Sheffield Star newspaper.
"I thought it was a stupid storyline and I copped a lot of flack over it. I was really upset. My contract didn't get renewed but I was pretty happy to leave by then. I was ready to go. I was 14 when I joined. It was time to leave."
Marsh is now living in London with his former co-star Ben Nicholas, who played Stingray Timmins. They have been auditioning for West End theatre roles and making personal appearances at universities across the country.