He is a tall and tanned man with a hawk-like nose. He has short, dark brown hair and a goatee. He was wearing two different suits, one of them being a cyan uniform with black accents and boots with his name and logo on it. The other was a silver diving suit with an oxygen pack and belts with pockets. This suit covered everything but his face.
Jonah was first seen in The Krakken, where he and his men pretended to be a fish saving organization, named The Friends of Fish. They fenced off a portion of the lake, which Captain Shaw found suspicious. Shaw wanted to cross the fence, but Jonah asked him to turn around. Soon after that, the Krakken Krakken attacked Jonah and his crew, who were saved by XLR8. The Krakken wanted a box from them (which was later revealed to contain one of her eggs).
Later, he was seen after his men took Shaw out of the water while he was searching for the Krakken. He asked Shaw what he was doing down there, but the captain refused to tell him and punched Shaw in the face. The men took Shaw to his ship, while Jonah dropped a tracking device into the water that would help him locate the eggs. In addition to this, he dropped a bomb onto Shaw's ship and destroyed it.
What he didn't know was that Ben with Shaw and heard everything. Ben turned into Stinkfly and followed them. In order to stop him, Jonah dropped oil barrels into the water and blasted them to detonate. This managed to get Stinkfly to the water where he tried to knock over him. Stinkfly managed to hide from them and save Shaw, who had been just thrown out by Jonah's goons.
At the Rust Bucket, Gwen looked up Melville's name and discovered his true story. He was a poacher who traveled around the world, poached rare animals, crated them up and sold them to private collectors. It was clear that Jonah Melville was an enemy to all wildlife.
Jonah was seen at a harbor where he managed to get the second egg too. He said that after he sold them to the highest bidder, he would be rich enough to move to the Bahamas. However, the Krakken appeared, which made him think to capture her too. He got in his submarine, while his men tried to hold up the Krakken. Before he could attack the Krakken, Ripjaw appeared and started to fight him. After a long fight, the eggs were taken from him and were given back to their mother. The Krakken destroyed his suit and was about to kill him but he was stopped by Ripjaws. The Krakken returned to her eggs and Ripjaws punched Jonah in the face, knocking him out cold. He was then hung on a stump and left for the police.