The search for Brian Laundrie was continuing in Florida's Carlton Reserve after his fiancée's death was ruled a homicide.
The Sarasota County Sheriff's Office said members of the Sheriff's Underwater Recovery Force have responded to the reserve, which is located in Sarasota County.
"This in addition to our Emergency Response Team, Air-1 & patrol," the sheriff's office tweeted.
"SURF Team members are divers called upon to search bodies of water for evidence," it said.
"These highly-trained deputies work in the most difficult and challenging environments imaginable. They are on call 24/7/365."
Laundrie, who is a person of interest in the case of 22-year-old Gabby Petito, remains missing over a week after his family said they last saw him.
Investigators have used ATVs, dogs, drones and more as part of their ongoing search for Laundrie at the reserve.
The swampy, wild landscape of the reserve has made the search particularly difficult.
"Please be aware, the Carlton Reserve is a vast and unforgiving location at times. It is currently (waist) deep in water in many areas," police said.
"This is dangerous work for the search crews as they are wading through gator and snake infested swamps and flooded hiking and biking trails."
Authorities also searched the family home on Monday after getting a search warrant for the property. FBI agents removed a number of items from the home and towed away a Ford Mustang convertible.
In addition, Laundrie's parents, Christopher and Roberta Laundrie, were questioned at their home by the FBI.