Tools of the Trade - USERT (Text Only)
FBI Dive Team
They work in what is often a dark, difficult environment that requires precision teamwork and equipment that supplies the very air they breathe. They are the members of our Underwater Search Evidence Response Team (USERT), and their efforts to recover a knife, gun, or an airplane’s black box, can be critical to an investigation.
Using a variety of specialized equipment, including sonar, metal detectors, and lift bags capable of raising a two-ton vehicle from the depths, team members working together above and below the surface can locate evidence as large as a jet engine and as small as a bullet buried in underwater dirt.
- Diving with a helmet and other gear, total weight of equipment on the surface can exceed 100 pounds.
- USERT members search to recover evidence or work on humanitarian missions. They are not a tactical team, like Navy SEALS.
- The team generally follows recreational diving limits, descending no deeper than 130 feet for non-decompression dives.
- Despite the usual pitch-black environment they work in, divers rarely use lights below the surface because particulate matter churned up from walking on the bottom diffuses any light. Instead, sonar equipment—usually controlled from the surface—is used to direct the divers and locate evidence.
- Divers must be in top physical condition. Walking the bottom with a current of 3 or 4 knots is as physically demanding as jogging on the surface.
Team members have three basic configurations for diving under various circumstances:
- Contaminated water: requires protective suit and helmet; air is supplied from the surface.
- Normal conditions: helmet not required; air provided from the surface through a mask.
- Normal conditions with SCUBA (self-contained underwater breathing apparatus): requires tank, regulator, and mask.
USERT is equipped with a variety of gear, from inflatable boats and larger vessels to underwater robotic vehicles and side-scan sonar units. The most important element to achieving its mission, though, is the teamwork between the divers in the water and the team operating on the surface.
Surface air supply connects to a three-hose, color-coded cord: yellow hose carries air; red hose carries communications wires; blue hose is the pneumofathometer, a depth gauge used so team members on the surface know divers’ depths at all times.
- Box allows surface team to run air and communications for two divers at one time.
- Attached speaker system allows for two-way communication between team members above and below the surface.
- Blue and orange hoses are connected to tanks on the surface. Potentially unlimited air supply can be achieved by using an air compressor instead of tanks.
Kirby Morgan 17B: weighs about 30 pounds, standard commercial diving helmet.
- Block (on the right side): allows diver to switch from surface air to emergency gas supply carried in tank on his back.
- Block switch: front switch ventilates helmet and prevents deadly carbon dioxide buildup; also functions like a portable air-conditioning unit to cool the diver’s face.
- Nose piece: allows diver to clear his ears while descending to equalize air pressure in the ear canal.
- Regulator: Venturi switch allows adjustment of air intake.
- Quad valve exhaust: allows air bubbles to exit the helmet when diver exhales.
- Inside helmet: blue hood designed for comfortable fit, includes chin strap.
- Ear speakers: enables communication between surface team and fellow divers.
AGA mask: full face mask uses positive pressure as opposed to a “demand” regulator.
- Most popular mask for commercial and military diving.
- Equipped with an oral-nasal cavity; regulator on side allows air to enter from left and bubbles to exit on right.
- Has valsalva capability for equalizing ears during dive.
- Two ear buds on either side of the mask allow for communications with other team members.
- Built-in snorkel capability for surface work.
- Buoyancy Compression Device (BC): A vest-like device with a wing on the back that can be manually inflated or deflated to control buoyancy; also contains removable weight pouches. When diving with surface-supplied air, diver’s emergency tank connects to the BC.
- Emergency Gas Supply: An aluminum cylinder that weighs 32 pounds and contains 80 cubic feet of gas (21 percent oxygen) under 3,000 pounds per square inch (psi) of working pressure; provides about 30 minutes of air.
Dry Suit: Vulcanized rubber suit that keeps divers dry. Up to three layers of clothing can be worn underneath, depending on the water temperature and where they are diving. Dry suit seals to helmet for water-tight fit.
Fins: Made from hard rubber, equipped with spring snaps or quick-release units in back for easy entry and removal; fins are generally used when divers operate in stronger currents.
Lift bag: For safety reasons, divers are prohibited from lifting anything above 15 pounds by themselves. Lift bags inflate to lift objects as large as 2,000-pound vehicles. Bags are inflated either by divers or, for larger items, by surface-supplied air.
Depending on whether the mission is humanitarian—recovering bodies from a plane crash or shipwreck—or to recover evidence such as a weapon, the dive team employs an array of equipment, from metal detectors to underwater remotely operated vehicles.
Sector scan sonar on tripod with GPS grid: Provides 360-degree analysis of the bottom composition out to a maximum range of 300 feet.
- Self-righting tripod is dropped from the surface; sends signal to computers on the surface; surface team directs the divers where to search.
- Transducers send and receive sonar waves.
Side scan "Towfish" unit: Torpedo-like sonar designed to be towed behind or alongside a boat to cover wider search areas.
Boat: This 27-foot Boston Whaler is the primary dive platform for USERT. It is equipped with a dive door for easy on/off access for divers and has a crane-like device called a davit that allows the boat to winch a large remotely operated vehicle on and off the deck.
Remotely Operated Vehicle (ROV): Units come in various sizes and are generally equipped with thrusters, lights, a camera that can transmit high definition images directly to the surface, and an “articulator” or manipulator that can grab small objects.
Light and camera system on pistol grip: Light burns so hot it can only be activated underwater. Lights and recording function are controlled from the surface, and high definition images are displayed on surface monitors.
Metal detector: Box mounts on the diver’s air cylinder.
Whip: Circular wand allows divers to locate large and small objects; stowed around emergency tank when not in use.