The DIR Glossary: 60 Terms in Plain English

Every system has its vocabulary, and DIR has more than most. This glossary defines the terms you'll meet in DIR and UTD training, in plain English, with links to the articles that explain them properly.

A–B

All usable. The gas rule for dives where you don't need to return to the start, such as a drift dive with a live boat: all gas above rock bottom can be used. See Gas Management.

ATA (atmospheres absolute). Pressure including the atmosphere. In salt water, depth in feet ÷ 33 + 1.

Back kick. A kick that moves you backward without disturbing the bottom. See How to Back Kick.

Backplate. A rigid steel or aluminum plate that holds the cylinder on your back and anchors the harness and wing. See Choosing a Backplate and Wing.

Backup light. A small light clipped to a chest D-ring, ready if the primary fails. One for open water, two for overhead dives.

Balanced rig. A rig weighted so you can hold a shallow stop with near-empty cylinders and still manage the full rig if your wing fails at depth. See What Is a Balanced Rig.

Basic Six. UTD's six foundation skills: regulator remove and replace, regulator exchange, regulator recovery, a modified S-drill, mask clearing, and mask remove and replace.

Bubble check. A teammate checks your valves, first stages and hoses for leaks just after the descent starts. See Pre-Dive Checks.

D–E

Deco bottle. A cylinder of decompression gas, such as nitrox 50 or oxygen, carried on the left side and marked with its maximum operating depth.

Depth consumption rate (DCR). Your gas use per minute at depth: your surface rate multiplied by the pressure in atmospheres.

DIR (Doing It Right). A holistic approach to diving built on fundamental skills, a standardized minimal configuration, team procedures and gas planning. See What Is DIR Diving?

Ditchable weight. Lead you can remove underwater, such as on a belt, as opposed to a steel plate or cylinders.

Doubles. Two cylinders, either joined on your back by an isolator manifold or carried at your sides in sidemount. See Sidemount vs Backmount.

Equivalent narcotic depth (END). How narcotic a gas is, expressed as the depth where air would feel the same. UTD keeps it at 100 feet or less and counts oxygen as narcotic.

Essentials. UTD's skills courses for certified divers: Essentials of Recreational Diving and Essentials of Tech. See UTD Essentials: What to Expect.

F–G

Frog kick. The main DIR kick: a sweep of the fins that pushes water behind you, followed by a glide. See How to Frog Kick.

GLADDDDD. UTD's pre-dive plan review: Goal, Leader, Air/gas, Depth, Duration, Deco, Direction and Distance.

Gradient factors. Settings that control how close a Bühlmann-based computer lets you get to its model limits. See Gradient Factors Explained.

GUE (Global Underwater Explorers). A training agency whose curriculum is built on DIR. See GUE vs UTD vs Hogarthian.

H–I

Halves. The gas rule for dives where returning to the start is preferred but not essential: after setting rock bottom aside, spend half the usable gas going out.

Helicopter turn. A kick that rotates you in place without moving forward or back. See Helicopter Turn and Modified Flutter.

Hogarthian. The minimalist equipment configuration at the root of DIR, named for cave diver William Hogarth Main. See Hogarthian Configuration Explained.

Hogarthian harness. One continuous piece of webbing through a backplate, with one buckle, a crotch strap and a few D-rings. No quick releases.

Isolator. The valve in a doubles manifold that joins or separates the two cylinders. Closing it can limit gas loss from an affected side; the actual gas preserved depends on the failure, pressures and valve state.

L–M

Long hose. The primary regulator's hose, 5 or 7 feet long under UTD standards (7 feet for Gardner Underwater training), donated to a teammate who's out of gas. See Long Hose Configuration.

Manifold. The crossbar joining backmount doubles, with an isolator valve in the middle.

Maximum operating depth (MOD). A depth limit based on the selected oxygen partial-pressure ceiling. Other limits, including narcosis, gas density and qualification, can require a shallower dive. Deco bottles carry MOD markings.

Min Deco. UTD's no-decompression limits and standard ascent strategy for recreational dives.

Modified flutter. A compact flutter kick from the knees and ankles, for tight spaces and fine silt.

Modified frog. A smaller frog kick driven from the knees and ankles, for moving gently near the bottom or your team.

N–O

Necklace. The bungee loop that holds your backup regulator under your chin. See Bungeed Backup Regulator.

Nine failures. UTD's set of backmount valve failure scenarios, from a fixable right post failure to an isolator closed or a post rolled off. See The Valve Drill Explained.

Nitrox 32. A standard gas of 32 percent oxygen, used to 100 feet.

Overhead environment. Any place where you can't ascend directly to the surface, such as a cave or wreck interior. A separate training category in UTD.

Oxygen partial pressure (PPO2). The pressure of oxygen in a gas at depth. UTD's bottom mixes target 1.2 on average with a maximum of 1.4; decompression gases go to 1.6.

P–R

Post (right and left). The valves on each cylinder of backmount doubles. The right post feeds the long hose and wing; the left feeds the necklace backup and gauge.

Primary light. The main dive light, used for communication as well as seeing, often with a canister on the right hip.

Ratio Deco. UTD's method for planning and adjusting a decompression ascent during the dive, using standard gases. It applies existing decompression models rather than being a new one.

RMV (respiratory minute volume). Your surface-normalized gas-consumption rate, in cubic feet per minute or liters per minute. See How to Calculate Your SAC Rate and RMV.

Rock bottom. The gas reserve two divers need to reach the surface or the next gas source while sharing one supply, from the worst point of the dive. See the Rock Bottom Calculator.

S

S-drill. UTD's practiced gas-sharing drill: donate the long hose, switch to the backup, stabilize and move together. See Out-of-Air Drill.

SAC rate. Surface air consumption, often expressed in psi per minute for a particular cylinder.

Sidemount. Cylinders carried at your sides instead of on your back.

SMB (surface marker buoy). An inflatable buoy sent to the surface on a line to mark the team's position. See How to Deploy an SMB.

Spool. A compact line holder used to deploy an SMB.

Stage bottle. An extra cylinder of bottom gas carried on the left to extend a dive. Unlike a deco bottle, it doesn't carry depth markings.

Standard gases. A short list of mixes the whole team uses for each depth range. See Standard Gases.

Surface consumption rate (SCR). UTD's term for your gas use per minute at the surface, as a volume.

T

Team. Two or three divers diving as one unit, with one plan and one configuration. See Team Diving vs Buddy Diving.

Thinking diver. A diver who understands why each practice exists, not just how to do it; UTD contrasts it with a "protocol diver." See What Is a Thinking Diver?

Thirds. The gas rule for dives where you must return to the start: after setting rock bottom aside, spend a third of the usable gas going out. See The Rule of Thirds.

Trim. Your body angle in the water. DIR divers aim for horizontal. See Horizontal Trim.

Trimix. A gas of oxygen, helium and nitrogen, written oxygen first: 21/35 is 21 percent oxygen and 35 percent helium.

Turn pressure. The pressure at which the team turns the dive, set before the dive by the gas rule.

U–Z

Usable gas. All gas above rock bottom.

UTD (Unified Team Diving). A training agency that grew from Hogarthian and DIR roots and unifies backmount, sidemount and rebreather diving in one system.

Valve drill. A practiced sequence for reaching and operating your cylinder valves while staying in trim. See The Valve Drill Explained.

Weight check. The end-of-dive test of your weighting: hold a shallow stop with a nearly empty cylinder and an empty wing. See How Much Weight Do I Need?

Wing. The buoyancy cell between your backplate and cylinder. It balances the rig; your lungs do the fine buoyancy work.

Z-System. UTD's sidemount system, whose harness manifold keeps the long hose and necklace setup the same as backmount.

Learn the language in the water

The fastest way to learn the vocabulary is to use it. Browse all of our courses, or start with Essentials of Recreational Diving.