In one episode he reeled in a Queensland grouper.
"This thing really is a river monster," Wade said.
For the show, Wade travels the world to find the biggest, strongest, deadliest -- and, well, weirdest -- freshwater fish you've never heard of. Which is kind of the point. They're so elusive and mysterious, they're almost mythical.
Wade landed an elusive goonch catfish in the Kali River of northern India.
"That is a big fish," he said. "They do exist, the Goonch do exist."
In the Amazon River, he caught a paraiba.
"This is the one I wanted, the paraiba, the real monster of the Amazon," Wade said. "This is the one that people say when it gets big enough it goes after people as well."
In the Mekong River in Thailand, Wade went after the legendary giant freshwater stingray -- only it was more than a legend.
The one Wade caught measured six feet across and weighed about 400 pounds.
So when "Nightline" heard Wade was visiting New York, we dared him to visit the edge of what we consider a mythical body of water -- Manhattan's East River -- to see what gilled creature he could pull out alive ... no doubt something really exotic.
We asked Wade if he had ever fished in New York City waters before.
"No, I haven't, no, this will be my first time," Wade said. "In fact this is exotic for me, very exotic. Believe it or not."
The East River is actually quite glorious, crowned by architectural gems like the Brooklyn Bridge. For his fishing spot, Wade ducked under the Queensboro Bridge, with road traffic 20 yards away and boat traffic all over the place.
"It's very different than what I normally do," Wade said. "Normally I'm in a rainforest or mountains. Urban -- I don't know about the idea of that."
But what could be down there? And whatever it might be, could Jeremy Wade find it, hook it and pull it out?
For starters, Wade did what he always does when he sets out on a hunt: He met a member of his own team. In this case it was New York City fisherman Ryan Chaffo.
"Some people see me walking down here with a fishing rod and go, 'Where are you going?'" Chaffo said. "And I'm like, 'The river.' And they're like, 'The East River?' And I'm like, 'Yeah, do you know another one on this side of the island?'"
Wade wanted to know what the water was like.
"Well, right now we're low tide," Chaffo said. "Whenever the current really starts to move it will actually be about four knots, so quite fast."
"I'm surprised how clean it is," said Wade.
"This being the East River?" laughed Chaffo.
"Well, this is, so it's tidal here so, no -- I was expecting dead bodies and..." Wade said.
The fishermen got down to business. For the outing they had a bona fide New York City soundtrack -- a helicopter that just wouldn't seem to go away.
"Normally when you go fishing you have to creep around really quiet so that you don't scare the fish," Wade said. "Not an issue here."
"Yeah, here they don't really seem to be thrown off by traffic or helicopters," Chaffo said. "I mean that's all day, every day for them."