How the oral works
There usually isn't a separate sit-down oral. The examiner asks questions throughout the practical exam: at the chart table, on deck, and often in the evening with flashcards of lights and shapes. Expect anything from the syllabus, plus detailed questions about the passages in your own logbook.
Answer clearly, give your reasoning, and say so if you're unsure rather than guessing. Examiners are checking that you'd be a safe skipper, not that you can recite rules word for word. See the pre-exam requirements if you haven't booked yet.
Collision regulations
Two sailing vessels are converging with the wind on different sides. Which one gives way?
The one with the wind on her port side keeps out of the way (Rule 12). With the wind on the same side, the windward vessel gives way. If you're on port tack and can't tell which side the other vessel has the wind, assume you're the give-way vessel.
You're motor-sailing. What are you under the rules, and what do you show?
A power-driven vessel, because you're propelled by machinery. By day you should show a cone, point down, forward where it can best be seen (Rule 25). By night, masthead light, sidelights and sternlight, not a tricolour.
When are you overtaking another vessel?
When you come up on her from more than 22.5 degrees abaft her beam, the position from which at night you'd see only her sternlight. The overtaking vessel keeps clear until finally past and clear (Rule 13), and that applies to a sailing yacht overtaking a ship too.
How do you know if a risk of collision exists?
Take a series of compass bearings: if the bearing doesn't appreciably change while the range closes, there is a risk (Rule 7). Risk can still exist with a changing bearing when approaching a very large vessel, a tow, or anything at close range. If in doubt, assume it exists.
What does Rule 9 require of a yacht in a narrow channel?
Keep as near to the outer limit of the channel on your starboard side as is safe and practicable. A vessel under 20m, or any sailing vessel, must not impede a vessel that can safely navigate only within the channel.
How should you cross a traffic separation scheme?
On a heading as nearly as practicable at right angles to the general direction of traffic flow, so you spend as little time in the lanes as possible and your aspect is clear to ships (Rule 10). Under 20m or under sail, you must not impede a power-driven vessel following a lane.
Go deeper: COLREGS steering and sailing rules explained · COLREGS Rule 19: conduct in restricted visibility
Lights, shapes and sound signals
At night you see an all-round red light over an all-round white, and a green light below them. What is it?
A vessel engaged in fishing (other than trawling), making way through the water, and you're looking at her starboard side. A trawler would show green over white.
Red over white over red, all-round, in a vertical line?
A vessel restricted in her ability to manoeuvre, such as a dredger, survey vessel or one laying cable. By day she shows ball, diamond, ball.
Two all-round red lights in a vertical line?
A vessel not under command. If she's making way, she adds sidelights and a sternlight. By day, two black balls.
What's a black cylinder by day?
A vessel constrained by her draught (Rule 28). At night she may show three all-round red lights in a vertical line in addition to the normal power-driven lights.
A sailing yacht under 20m: what lights can she show?
Sidelights and a sternlight, which may be combined into a single tricolour lantern at the masthead. She may also show all-round red over green at the masthead, but never together with the tricolour. Once the engine is running she's power-driven and shows the steaming light instead.
In fog you hear one prolonged blast followed by two short. What could it be?
A sailing vessel, or a vessel not under command, restricted in her ability to manoeuvre, constrained by her draught, fishing, or towing or pushing another vessel (Rule 35). A power-driven vessel making way sounds one prolonged blast at least every two minutes.
What does five or more short and rapid blasts mean?
I am in doubt whether you are taking sufficient action to avoid collision (Rule 34(d)). It may be supplemented by at least five short and rapid flashes of light.
Go deeper: Navigation lights and day shapes, explained · COLREGS sound signals explained
Buoyage
You see six quick flashes followed by a long flash. What is it, and where do you pass?
A south cardinal mark, so the safe water is to the south and you pass south of it. The long flash makes the six unmistakable from the east's three and the west's nine.
Describe an isolated danger mark.
Black with one or more broad red bands, with two black balls as a topmark and a white light flashing in groups of two. It sits on a small danger with navigable water all round it.
Describe a safe water mark.
Red and white vertical stripes with a single red ball topmark, showing a white isophase, occulting, single long flash every 10 seconds, or Morse A light. It marks the start of a channel or a landfall, with navigable water all round.
Go deeper: IALA buoyage: lateral marks explained · Cardinal marks: topmarks, colours and lights
Tides
What's the rule of twelfths, and when wouldn't you trust it?
The tide rises or falls 1, 2, 3, 3, 2 and 1 twelfths of its range in each of the six hours either side of high water. It assumes a symmetrical tide, so don't rely on it where the tidal curve is distorted, such as the Solent and the coast between Swanage and Selsey. Use the port's tidal curve instead.
What's the difference between springs and neaps, and why does it matter?
Springs come a day or two after new and full moon, with the largest range and strongest streams. Neaps come around the quarter moons, with the smallest range and weakest streams. It changes your depths, your tidal gates and how hard races and overfalls run.
How do you work out your clearance under the keel?
Charted depth plus height of tide gives the depth of water. Take off your draught to get the clearance. Over a drying height, the depth is the height of tide minus the drying height.
Why does wind against tide matter?
When wind and stream oppose, the sea becomes short and steep, especially off headlands and in races. Plan to round headlands when the stream runs with the wind, or at slack water.
Passage planning and pilotage
Talk me through planning an overnight passage.
Weather and its trend, tidal streams and any tidal gates, dangers along the route and clearing lines, waypoints, the lights you expect to see and their characteristics, ports of refuge, a watch system for the crew, fuel and water, and a pilotage plan for the arrival port. Then a crew brief before you leave.
What's a clearing bearing?
A bearing on a charted object that keeps you clear of a danger, for example 'keep the lighthouse bearing more than 045°T'. As long as the bearing stays on the safe side of the limit, you're clear.
What are the limitations of radar and AIS?
Radar can miss small craft, especially in sea clutter or rain, and you mustn't make assumptions from scanty information (Rule 7). Not every vessel carries AIS, data can be wrong or out of date, and AIS doesn't replace a proper lookout.
Weather
What happens as a warm front approaches and passes?
Ahead of it, pressure falls, cloud thickens and lowers, the wind backs and increases, and rain sets in. As it passes, the wind veers, the rain eases to drizzle, the temperature rises and the pressure fall slows. Visibility is often poor in the warm sector.
And a cold front?
The wind veers, often sharply and with squalls, heavy rain or showers arrive, the pressure starts to rise and the temperature drops. Visibility usually improves behind it.
What causes a sea breeze?
On a sunny day the land heats faster than the sea, warm air rises over the land and cooler air flows in from the sea to replace it. It builds through the afternoon and dies in the evening.
Where would you get a forecast at sea?
The Coastguard's VHF maritime safety information broadcasts (announced on channel 16), NAVTEX, the BBC Radio 4 shipping forecast, and online sources such as the Met Office when you have a signal.
Safety and emergencies
When would you send a Mayday rather than a Pan-Pan?
Mayday when a vessel or person is in grave and imminent danger and needs immediate assistance, such as sinking, fire or a man overboard you can't recover. Pan-Pan for an urgent situation without imminent danger to life, such as a disabled engine near a lee shore. Sécurité is for safety information like a navigational hazard.
Someone goes overboard. What are your first actions?
Shout 'man overboard', throw a lifebuoy or danbuoy, press the MOB button on the plotter, and put one person on pointing and nothing else. Then manoeuvre back under your chosen method and have a plan for getting them aboard, which is often the hardest part. Send a DSC alert and Mayday if they aren't quickly recovered.
When would you abandon ship to the liferaft?
Only when the yacht is definitely lost: you should step up into the raft. A damaged yacht is still a bigger, more visible refuge than a liferaft. Take the grab bag, EPIRB or PLB and a handheld VHF.
What would you cover in a crew safety brief?
Lifejackets and harnesses, jacklines and clipping on, man overboard drill, fire extinguishers and the fire blanket, gas safety, the liferaft and grab bag, how to send a distress call on the VHF and DSC, flares, the first aid kit, seacocks and bilge pumps, and starting and stopping the engine.
Go deeper: How to send a Mayday or Pan-Pan on VHF
Engines
The engine is overheating. What do you check?
Whether water is coming out of the exhaust. Then the raw water seacock is open, the strainer is clear, the impeller is intact, the belt is tight and the freshwater coolant is topped up.
The diesel stops and won't restart. What are the likely causes?
Almost always fuel: an empty tank, a blocked filter, water in the fuel or air in the system. Change the filter, drain any water and bleed the fuel system.
About you and your passages
Be ready to talk through your longest passage, a time the weather turned, and how you ran your crew. The examiner is checking your logbook is real and that you learned from it, so specific details beat general claims.