shark experts paul and james glancy know what i'm talking about. >> i know what it's like to be eatenit sucks. >> reporter: he's a former australian navy diver who lost an arm and a leg to a bull shark in 2009. in the show "shark wrecked," airing tomorrow on discovery, the divers put themselves in extreme conditions. at one point they're in a recreated shipwreck. then simulating what it would take to survive in shark-infested waters. out in the middle of the sea, the two are trying to stay afloat. and at one point they got company and have to fend off a team of tiger sharks. >> as nighttime came, it started to get a lot more stressful. just in the twilight when the sharks knew it was low light levels, there's no way we can see the sharks coming at us until it was the very last second. we had a netted tent to get into if it became too dangerous. we got into that. >> they started far away, then get closer and closer and closer, up to the point we're literally pushing them away, having to physically push them away with our fins, our hands, anything, just to keep them behind us. >> report

two ex-military men james glancy and paul de gelder.counter with a bull shark that cost him an arm and a leg. >> i was minutes away from death and people probably think i'm a bit crazy by doing this. >> reporter: even though the nearest hospital is more than 100 miles away this pair dives incoming face-to-face with an army of sharks. finally after 43 hours and 21 minutes, paramedics made the call. it was time to pull the men out of the water. but you don't have to be a military man to participate in shark week. five "naked and afraid" all stars will have to go without clothing and s on an island surrounded by shark infested waters surviving exclusively on what the ocean provides. >> all right, paul, the guys in the water, those two are just fine. dehydrated. in good health. they might do this once again. >> playing with fire they are, especially the one who survived an attack. >> a hundred miles away that hospital, too, that's dicey. all right, good luck to them. >> for more shark stories tune into shark week on discovery. coming up, it