Transcript for Testing a 'shark suit' that lets divers get up close without cage
Steely eyed, sharp toothed predators that can appear without any warning. Watch out, Jeremiah. Careful, guys. They're coming in from every direction now. This is not good. Watch out, camera. Reporter: Sharks strike fear into just about everyone, except this guy, Jeremiah Sullivan. I don't know that I'm the shark man. I'm just another guy. Reporter: A marine biologist, Sullivan has been studying sharks closely for decades, very closely. Big tiger coming in slowly but deliberately. She tried to push past me. Wow. Whoa, she's come back already. Hang on now. Reporter: 40 years ago he created the shark suit, a protective armor that would allow him to study sharks free of cages. It's important to study them in their own environment, not from a cage, which can alter the very behavior you're trying to study. Reporter: The original was made of chain mail, but they've never been able to withstand the biggest shark bites. So now he's putting his latest version of the suit to a test in the nat geoshow, "Man versus shark". No cages. No second chances. These sharks are going nuts already. Just man versus shark. Reporter: You're putting your own body on the line, risking your own life for this. You know, I don't consider it that kind of a threat, because I have so much familiarity with what's going on, I have a pretty significant level of confidence that this new type of armor would work. What I'm trying to do is get away from all the chain mail. This is the old suit. You'll notice the difference between black mail. Frequently the shark's sides are silvery. If you've got a piece of fish in your hand, it looks very similar to your hand. As the shark comes in for the fish, he can easily chew on you. Reporter: I will never wear a silver bathing suit again. You see how heavy this metal is. They're heavy, expensive, quite durable but not perfect. I'm shifting over to these advanced laminates. Reporter: Looks sort of like a shin guard. Nothing is going to be able to get anywhere through here. Reporter: To test it, Sullivan engages with some of the most dangerous sharks known to man. Jeremiah! Oh, that was a close one. Reporter: Even baiting tiger sharks. Tiger coming in. Got it, 180 pounds. Big shark, powerful shark. They eat most anything. Their teeth, as you request see here are quite different. They've got this backward edge. They have a thicker tooth, and they're used to biting into things that are harder, like turtles. This is the species you hear the famous stories about ate a keg of nails or license plates, that's tiger sharks. Reporter: Jeremiah gets bitten by a tiger shark on purpose. They're getting more revved up. Careful guys. They're coming in from every direction now. This is not good. Reporter: After meeting Jeremiah, I suited up for my own close encounter with the sharks at the Long Island aquarium. Moment of truth. We are swimming with sharks, and as great as Jeremiah's suit sounds, I'm pretty glad to be in this cage. Ah! I can't believe how close he is right now. How many sharks are in this tank? There's ten total. Reporter: Whoa, that one caught me by surprise a little bit. They kind of sneak up on you. Yeah, they're silent, silent hunters. You don't see them coming. Reporter: Okay, that's enough shark experience for me. Back on dry land I get some practical tips from the shark whisperer. The golden rule with shark divers generally is it's the shark you don't see that's going you. Reporter: Are there things you can do to stay safe? Yes, yes. If you're in murky water it's very dangerous. I stay out of murky water when I know there are sharks that are potentially biters. Reporter: Murky water is a no-go. If it's clear water, if you panic and move around and in an erratic way, you look like a struggling fish or animal that may be injured or sick. That's what predators look for. In the ocean, if sharks do come around, it's very easy if you can stay cool and focussed. Simply redirect them away from you. It's that simple. Reporter: Keywords. If you can stay cool, which not a lot of people can do when they're face-to-face with a shark. I know that probably sounds silly, but that's the best chance you've got. Reporter: As more people flock to the oceans close encounters will only become more is there something individuals can do to mitigate this increase? No. Inform yourself. That's all you really can do. You can't expect sharks not to behave like sharks in their home. Reporter: For "Nightline," Diane Macedo in river head, new York.
This transcript has been automatically generated and may not be 100% accurate.