1. World's Biggest Stingray

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. 7 July 2014. 44 min

Thailand's giant stingrays and the whip rays of Australia can grow up to 16 feet and 1,300 lbs.

2. River Wolf

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. 14 July 2014. 44 min

Wolf fish, known locally as haimara, can reach a metre in length and is said to hunt humans.

3. Amazon Shocker

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. 21 July 2014. 44 min

There's a freshwater fish with a shock five times more powerful than a US wall socket.

4. Frankenfish

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. 28 July 2014. 44 min

The Thai snakehead is said to be able to move on land, and has apparently spread to US waters.

5. Silver Devil

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. 4 August 2014. 44 min

In Nicaragua, Zeb faces his most difficult battle hunting for one of the biggest monsters.

6. River Jaws

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. 11 August 2014. 44 min

Some shark species can survive in freshwater as well as salt.