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?
River Monsters: The East River Challenge
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."
River Monsters: The Waiting Game
The anglers used small fish and blood worms as bait.
"What's the take like?" Wade asked.
"Like a ton of bricks," Chaffo replied. "It's going to pull straight to the bottom."
And then they ... well ... they wait. Something all fishermen, Wade included, are all too familiar with.
On a trip on the Congo River to catch the ruthless, six-foot, 100-pound Goliath Riger fish, Wade waited for three weeks.
It wasn't until after visiting a witch doctor that Wade finally landed one of the fearsome fish.
Wade said that when he's shooting, a lot of time can pass just waiting.
"We could be filming for say two-and-a-half weeks," Wade said. "Normally fish don't respond on cue. You've got to hang around for a bit. ... It's a bit like looking for the Yeti or the Loch Ness monster, but you actually do get to see it."
Chaffo was pretty encouraging that the pair would get something any minute. In fact, the minutes started dragging into hours. At least that was plenty of time for Wade to talk about how he got into fishing.
River Monsters: Memorable Catches
"Well, it started with fishing in a river near my home in England," he said. "When I started I was 7 or 8. Then I sort of fished intensively throughout my teens and early 20s, you know, probably too much for my own good. I mean it was a bit obsessive.
"I think it's quite similar to a gambler," he said. "It's never going to be totally predictable, and you're always left thinking, if I just go tomorrow I'm going to get a bigger fish."
And Wade remembers all of those big and bigger fish that he has caught, with a sort of fondness -- and a hint of pride.
"This payara," he said. "Various other names, one is vampire fish because it's got these fangs, but they're on the lower jaw so you've got two long fangs on the lower jaw. And they are so long, that when it closes its mouth, they actually recess inside its head."
Then there was the alligator gar.
"Now that was in Texas on the Trinity River, and I think that's a very good example of how something can be right under your nose and you don't even know it's there," Wade said. "A lot of people, you know, living in Houston, have no idea these things are in their river."
Once, Wade even allowed himself to be the bait.
He jumped into a pool full of piranhas.
"If piranhas aren't hungry you can swim with them," he said. "Now, being television, my director said, 'On that shoot, well, you've got to demonstrate that, it's television, it's not radio, it's not a book. I got in the water, OK, I'm in the water -- can I get out now?"
And Then at Last...
Four hours later, we assure Wade, who has a plane to catch, that he shouldn't worry about catching a fish in the East River -- he should leave whenever he wants to. But that, of course, is not an option. He didn't want to give up.
And after six hours they landed a beautiful striped bass.
"Not bad for the East River, huh?" Chaffo said.
"I was starting to think you were making this up, that there weren't any fish in this river," Wade said. "This is actually the first one of these I've seen in the flesh."
And then he threw it back.