Even what we all go through at the tsa checkpoint you have to wonder how is it a lost jet skier in swim trunking and life jacket could penetrate the runways of one of the busiest airports in the... See More
Even what we all go through at the tsa checkpoint you have to wonder how is it a lost jet skier in swim trunking and life jacket could penetrate the runways of one of the busiest airports in the nation? It's an incredible story of lapse security and only abc's jim avila has it. Reporter: Daniel casillo lost in his prize jet ski exposed a multimillion dollar system at new york's jfk and he wasn't even trying. The whole intention was to be seen because you're in the airport. There's not to be some type of security. They have motion detectors. Reporter: Afc an unintended test of all those things, even the airport barbed wire, chain link eight-foot perimeter fence that he easily climbed in his shorts and life vest. That was easy? There was no challenge at all. Reporter: How did this young man become both a trespassing pain in the new york authority's neck and unofficial security consultant for one of america's largest airports? It started on an august night in jamaica bay off the shoreline runways of jfk. The jet ski just shut off. I looked around. No lights. No boats, nothing. No noise, just pitch black. He's miles away from the shore in choppy water but heads toward faint lights in the distance swimming behind the dead water craft pushing it towards land. It takes hours. The actual tower as you can see that was my landmark, the only thing lit up I could go to. Reporter: Finally reaching it hoping just being that close to the airport would set off alarms and lead to rescue. I expected maybe a helicopter. Maybe a boat, something. Nothing happened. Reporter: Nobody patrolling -- I had nothing, nothing at all. I made a decision I'll have to get found. I'll have to take it upon myself to get over this fence to get seen. Something's got to happen. Reporter: Now you're inside the perimeter of the airport. Yeah, unfortunately, I was in the airport. Reporter: No alarms go off. Nothing. Reporter: So danny keeps walking towards the tower, crossing, he says, at least one active runway and taxiway. I walked right across it without any type of problem. I didn't get seen. Reporter: In fact his journey only ended horrifyingly enough when he reached the delta terminal 3 passenger terminal where he turned himself in to a baggage handler. I had to walk up to a cargo walker. That's jfk international airport. I walked to the terminal. That's crazy. Reporter: America's airports are not as secure as the public may think. From rogue pilots climbing the fence at st. George, utah and driving a jet into the terminal or this 2010 wild ride at dallas' love field. Tower, what's the protocol? Reporter: Clearly many experts say the jaw-dropper at jfk signals something must be done. It's time t relook at perimeter security. These are early warning signs, and what the bad operators are out there doing are they're studying, and that's what bad guys spend their time doing. They spend their timeopponent. Reporter: He got no rewards. Charged with felony trespassing ultimately reduced to a misdemeanor violation. He now threatens to threaten the port authority for what he calls harsh treatment. You would think someone that nt through what I went through would get medical attention, a cup of water, something. I got nothing. Reporter: He never told prosecutors he was mistreated and he wasn't. In a statement they claim he was offered medical treatment and will fight what he says are his false claims. Danny believes he deserves better. This is a major topic. This is a big deal. I didn't mean to do this. But I exposed sometng really important and that's a flawed security. Reporter: The port authority and raytheon say they are being corrected and increased patrols and working to make sure someone more serious than a lost jet skier never walks across runways at the jfk terminal again. For "nightline," I'm jim avila in new york.
This transcript has been automatically generated and may not be 100% accurate.