PADI Divemaster Theory cheat sheet

Divemaster liability rests on the duty of care: act within certified training, follow the standards, and never supervise beyond your rating or insurance coverage.

Ratios for certified divers under a Divemaster's supervision vary by environment and operator; open-water guided groups are commonly kept to about 8 divers per professional, with fewer in low visibility, current, or cold water.

The role is supervisory, not instructional: a Divemaster may lead certified divers, conduct Scuba Review, and act as certified assistant, but may not teach open-water courses or certify divers.

Pre-dive briefing content: site layout, entry/exit, depth limits, planned route, turn pressure, emergency procedures, buddy assignments, and recall signals.

Buddy checks before every entry: air on and valve position, BCD inflation, weights secured, releases fastened, and final OK - verified by the diver, then confirmed by the buddy.

Supervision is active: maintain head counts at entry, exit, and after surfacing; position yourself to see the whole group; dive the plan rather than following the least experienced diver's depth.

Incident response order: stop the dive, establish surface support, provide rescue breathing or oxygen if needed, activate emergency services, then document times, depths, and actions taken.

Divers missing at the surface: allow a short surface search, then begin a underwater search pattern from the last known point, considering drift, current, and elapsed time.

Record keeping matters: log professional dives, certification dates, and continuing-education status; most leadership ratings require current rescue training and a minimum logged dives.

A certified assistant works under the direct supervision of an instructor; the instructor retains responsibility for student safety and evaluation at all times.

Typical assistant tasks: set up and check student equipment, demonstrate skills, supervise practice stations, model correct behavior, and give feedback that supports the instructor's briefing.

Skill demonstration standard: perform each skill slowly, neutrally buoyant where appropriate, in clear view, and in the sequence taught - students copy what they see, not what they hear.

Common student problems and fixes: mask flooding from a poor seal (hair, strap, or nose), buoyancy loss from trapped air in the BCD, and regulator free-flow from pressing the purge or a cold-water condition.

Confined-water sessions run in shallow water with students able to stand or with immediate instructor contact; skills progress from no-mask, regulator recovery, and buoyancy before open-water application.

During open-water training dives, assistants watch for students ascending too fast, losing buddy contact, or exceeding depth limits, and signal the instructor rather than intervening in a way that removes supervision.

Student stress signals include rapid breathing, wide eyes, refusal to descend, and clamped regulator; slow the pace, re-establish eye contact, and surface if the student does not settle.

Evaluation is the instructor's role: assistants observe and report, but do not sign off skills, certify, or make pass/fail decisions.

Pressure increases by 1 atmosphere (atm) for every 10 metres (33 feet) of seawater; absolute pressure = 1 atm surface + depth/10 in metres.

Boyle's law (P1V1 = P2V2 at constant temperature): gas volume halves at 10 m and is one-quarter at 30 m; this governs buoyancy changes, mask squeeze, and equalisation.

Dalton's law: total pressure is the sum of partial pressures; at 30 m each gas fraction is four times its surface partial pressure, which drives nitrogen loading and oxygen toxicity risk.

Henry's law: gas dissolves in liquid in proportion to partial pressure; this explains nitrogen absorption on descent and off-gassing during controlled ascents and safety stops.

Air composition is about 21% oxygen and 79% nitrogen; the nitrogen fraction is used for no-decompression limits and repetitive-dive planning.

No-decompression limits and surface intervals come from dive tables or a computer; ascend no faster than 18 m/min (60 ft/min) and make a safety stop of about 3 minutes at 5 m after deeper dives.

Buoyancy: an object floats when displaced water weight exceeds its weight; adding gas to the BCD increases displacement and lift, while wetsuit compression on descent reduces lift.

Sound travels about four times faster in water than in air, and light loses red wavelengths first with depth; do not rely on colour or apparent direction of sound underwater.

Heat loss is faster in water than air because water conducts heat roughly 25 times better; exposure protection and dive duration planning follow from this.

Rescue sequence: recognise the problem, assess the scene, establish buoyancy for yourself and the victim, then act - never become a second victim.

Panicked diver at the surface: keep your regulator in, approach from behind or below, establish positive buoyancy for both, and talk the diver into calm breathing before towing.

Unresponsive diver underwater: bring the victim to the surface at a controlled rate, establish buoyancy, check breathing, and begin rescue breathing or CPR with oxygen if trained.

In-water rescue breathing uses a pocket mask with a head-tilt/chin-lift; remove the regulator only when the mask is sealed, and continue while towing to the exit.

Tired diver tow: use a steady kick, keep the victim's head above water, and choose a technique that lets you watch the victim and the route to the exit.

Missing diver search: gather last-seen point, time, and air supply; use expanding-square, U-pattern, or circular searches suited to the site and visibility.

Equipment failure response: signal your buddy, switch to your alternate air source, and ascend at a controlled rate with a safety stop when air supply and conditions allow.

Emergency oxygen is the first aid for suspected decompression illness and near-drowning; provide 100% oxygen if trained and the equipment is available, and arrange evacuation.

Self-rescue skills include regulator recovery, mask clearing, weight-belt removal at the surface, and establishing positive buoyancy - practise these until automatic.

Site briefing covers entry and exit points, depth profile, hazards (current, surge, entanglement, boat traffic), marine life, and emergency access for help.

Buoyancy control is the primary conservation tool: divers who touch the bottom damage coral and stir sediment; keep a metre of clearance and secure dangling equipment.

Do not feed, handle, or ride marine life; touching removes protective mucus, and feeding alters behaviour and can cause injury to divers and animals.

Anchor and mooring damage is a major reef impact; use fixed moorings where provided and brief divers to avoid anchoring on coral.

Marine protected areas may restrict fishing, collecting, and even touching; check local rules before diving and follow them over personal preference.

Surface conditions and currents determine site suitability: check tide, swell, wind, and visibility before entry and set a conservative turnaround point.

Boat diving management: head counts before and after entry, a visible surface marker or flag where required, and a designated surface support person.

Debris removal should be done only when trained and safe; never remove living organisms or disturb the site to collect rubbish.

Leave-no-trace practice: take all rubbish out, avoid contact with the bottom, and report environmental damage or wildlife injury to the operator or local authority.