ground and flying drones over the 25,000 acres of swamplands of this florida nature reserve. specialized under water dive teams arriving to assist while high-water vehicles navigate through waist-deep water. >> physical searches like that and that type of remote were area present all kinds of problems. it's a marshy area. it's thick with foliage. it's very hard to get into certain spots. >> reporter: laundrie going missing after returning to the family home the couple shared with his parents without petito september 1st. the fbi is asking the public to help find laundrie. >> it is usually a sign that you have a very challenging manhunt on your hands. >> reporter: they are also seeking assistance to piece together the timeline of petito's final days. august 12th, petito sharing this photo on instagram. that's the same day a witness dialed 911 to report a domestic dispute between her and laundrie, prompting police to