Imagine sailing through a busy shipping lane at night: a cargo vessel bearing down from starboard, a fishing boat crossing ahead, fog rolling in. What do you do? Who gives way? What signals should you sound? What safety equipment must you have on board?
The answers to all of these questions are not left to guesswork or national custom. They are defined by two landmark international agreements that govern every vessel afloat: the International Regulations for Preventing Collisions at Sea (COLREGs) and the International Convention for the Safety of Life at Sea (SOLAS). Together, they form the legal backbone of global maritime safety, applicable to everything from supertankers to weekend sailing boats.
This article is for every sailor - recreational or professional - who wants to understand not just what these rules say, but where they come from, why they matter, and how to apply them practically on the water.
How we got here: a brief history of maritime law
For most of maritime history, the sea had no universal rules. Each nation, navy, and port operated according to its own customs, and collisions were disturbingly common. When steamships began replacing sail in the early 19th century, the problem intensified: faster, less maneuverable, and multiplying rapidly, steam vessels were involved in accidents that older maritime customs simply had no answer for.
The first regulations for preventing collisions at sea were drafted in 1840 in Trinity House, London, and enacted by the British Parliament six years later in the 1846 Steam Navigation Act. But these were domestic rules, applying only in British waters.
The turning point came in 1863. A new set of rules drawn up by the British Board of Trade, in consultation with the French government, came into force. By 1864, the regulations had been adopted by more than thirty maritime countries, including Germany and the United States - signed into law by President Abraham Lincoln.
These were the first truly international collision regulations, and they introduced concepts still recognizable today: colored sidelights (red for port, green for starboard) and the obligation for an overtaking vessel to keep clear of the vessel being overtaken.
The next major milestone came in 1889. The Washington Maritime Conference was the first major diplomatic effort to create a single, uniform system of signals and maneuvers for all nations, formalizing the principles of the give-way and stand-on vessel that remain central to COLREGs today.
Then came the Titanic. On the night of April 14-15, 1912, the "unsinkable" ocean liner struck an iceberg on her maiden voyage and sank in under three hours, killing more than 1,500 people. The disaster exposed catastrophic failures: too few lifeboats, no continuous radio watch, canceled lifeboat drills, and no coordinated international safety framework. As a result, delegates from 13 different countries assembled in London between November 1913 and January 1914 to establish international standards in shipping safety, looking at radiotelegraphy, shipping design and construction, safe shipping lanes, ice warnings, life-saving routines and appliances, and distress signaling. The result - signed in London on January 20, 1914 - was the first SOLAS Convention.
Collision regulations continued to evolve in parallel. By the 1960s, a new hazard had emerged: radar-assisted collisions, where vessels travelling at speed in poor visibility misread their instruments and struck each other with more force than ever before. The 1960 SOLAS conference addressed the new problem of radar-assisted collisions by integrating radar use into the rules, fundamentally changing navigation in low visibility.
A decade later, growing traffic density - particularly in the Dover Strait - made it clear that a wholesale revision was needed. One of the most important innovations in the 1972 COLREGs was the recognition given to traffic separation schemes.
The first such scheme had been established in the Dover Strait in 1967, initially voluntary, but the 1972 COLREGs made compliance mandatory. The modern COLREGs were adopted in October 1972 and entered into force on July 15, 1977, after sufficient ratifications by member states of the IMO.
Today, both COLREGs and SOLAS are administered by the International Maritime Organization (IMO), a specialized agency of the United Nations, and continue to be updated in response to new disasters and evolving technologies.
COLREGs: the rules of the road at sea
What COLREGs are - and who they apply to
COLREGs is a treaty-level rule set that tells vessels how to avoid each other, what lights and shapes to show, which sound signals to make, and how to behave in narrow channels and traffic schemes. It applies to all vessels on the high seas and connected waters, from tenders to superyachts and commercial craft.
This universality is important. COLREGs does not distinguish between a 50-metre motor yacht and a 6-metre dinghy - the same framework applies to both. If you are on navigable water connected to the sea, COLREGs govern your conduct. The regulations consist of 41 rules organized into six parts: General; Steering and Sailing; Lights and Shapes; Sound and Light Signals; Exemptions; and Verification of compliance.
Stand-on and give-way: there is no absolute right of way
One of the most widespread misconceptions in recreational boating is the idea of absolute "right of way." COLREGs do not work that way. COLREGs does not grant anyone absolute right of way. It assigns responsibilities to reduce ambiguity, then expects both vessels to avoid a collision if the other fails to act.
The rules designate two roles in every encounter: the give-way vessel, which must maneuver to keep clear, and the stand-on vessel, which must maintain course and speed - but only until it becomes clear the give-way vessel is not acting. At that point, even the stand-on vessel must take avoiding action. The sea does not reward the mariner who holds their course while a collision unfolds.
Encounter situations: overtaking, crossing, and head-on
- Overtaking (Rule 13): if you are coming up from more than 22.5 degrees abaft another vessel's beam, you are overtaking and must keep clear. Once overtaking, you remain the give-way vessel until past and clear, even if relative positions shift. When in doubt, assume you are the overtaking vessel.
- Head-On (Rule 14): two power-driven vessels meeting head-on must both alter course to starboard to pass port to port. When in doubt whether it is head-on, assume it is and act accordingly.
- Crossing (Rule 15): power-driven vessels crossing with risk of collision - the vessel that has the other on her starboard side keeps clear and avoids crossing ahead if possible. A useful way to remember this: if another vessel is on your starboard side and the bearing is not changing, you give way.
- Hierarchy of Vessels (Rule 18): not all vessels carry equal obligations. Power-driven vessels give way to sailing vessels, vessels engaged in fishing, vessels restricted in ability to maneuver, and vessels not under command. However, there is an important catch for sailors: a sailing yacht with its engine running - even with sails up - is classified as a power-driven vessel for the purposes of the rules and loses its priority accordingly.
Four rules every sailor must internalize
While all 41 rules matter, four form the practical bedrock of collision avoidance at sea.
- Rule 5 - Lookout: Rule 5 requires a proper lookout by sight and hearing, using all available means. In practice, that means eyes out of the wheelhouse, listening for signals, and making systematic use of radar and AIS where fitted. Autopilot is a steering aid, not a watchkeeper. Neither is checking your phone a substitute for scanning the horizon.
- Rule 6 - Safe speed: Rule 6 asks you to proceed at a speed that allows effective avoidance and stopping, taking visibility, traffic density, sea state, and background lighting into account. If fog rolls in or you enter a dense fishing fleet, reduce speed and be ready to maneuver. There is no fixed "safe speed" - it is always relative to conditions at that moment.
- Rule 7 - Risk of collision: Rule 7 calls for early use of plotting tools and, if fitted, radar long-range scanning. If the bearing of another vessel does not appreciably change, assume risk exists and act early. A constant bearing with closing range is the classic - and dangerous - signature of an impending collision.
- Rule 10 - Traffic separation schemes: major shipping areas are organized into lane systems, much like motorways at sea. Rule 10 gives guidance in determining safe speed, the risk of collision, and the conduct of vessels operating in or near traffic separation schemes. Small vessels crossing a scheme must do so at right angles to the traffic flow, keeping the lanes clear for the large ships using them.
Lights, shapes and the IALA Maritime Buoyage System
Part C of COLREGs governs what lights and shapes a vessel must display, allowing others to identify vessel type, status, and direction at a glance: an all-round white light on an anchored yacht, three vertical red lights on a vessel constrained by her draft, additional lights on a towing vessel. These are not mere formalities - they are the visual vocabulary that lets mariners build an instant picture of who surrounds them and what obligations apply.
Equally essential is the IALA Maritime Buoyage System, which standardizes the buoys, beacons, and lights used to guide vessels safely through coastal waters, harbors, and rivers worldwide. The IALA buoyage system is divided into two regions due to historical differences in maritime navigation practices.
Region A - covering Europe, Africa, and most of Asia - uses red buoys on the port side and green on the starboard side when entering a harbor. Region B - covering the Americas, Japan, and others - reverses this, using green for port and red for starboard.
The only difference between the two regions is the lateral color arrangement. Cardinal, Isolated Danger, Safe Water, and Special marks are identical in both regions. This is critical knowledge for any sailor moving between ocean basins: the red-right-returning convention of North American waters is precisely reversed in European ones. Getting this wrong in an unfamiliar port is not a minor error.
The system uses five core mark types: lateral marks indicate the sides of a navigable channel; cardinal marks use compass directions (north, south, east, west) to indicate where safe water lies relative to a hazard; isolated danger marks identify a specific hazard with navigable water all around it; safe water marks confirm open, unobstructed water; and special marks flag specific features such as traffic separation zones, aquaculture areas, or exercise zones.
Sound signals: speaking the language of the sea
In reduced visibility or during close-quarters maneuvers, vessels communicate through sound. COLREGs Part D standardizes these signals precisely so there is no ambiguity. Here are the essentials every mariner should know.
When vessels are in sight of one another, one short blast means "I am altering course to starboard"; two short blasts mean "I am altering course to port"; and three short blasts mean "I am operating astern propulsion". Five or more short and rapid blasts is the doubt or danger signal - use it when another vessel's intentions are unclear or a collision feels imminent.
In restricted visibility - fog, heavy rain, limited sight - a power-driven vessel making way sounds one prolonged blast every two minutes; a vessel stopped and making no way sounds two prolonged blasts with a pause between them; a sailing vessel, vessel not under command, or vessel with limited maneuverability sounds one prolonged and two short blasts every two minutes.
Horns are not for expressing frustration. They are a formal language - and using them correctly, or recognizing them when another vessel does, can prevent a collision in the moments before anything else is possible.
Making your maneuvers readable
A practical principle runs through all of COLREGs that no rule explicitly states but every rule implies: your actions must be early, substantial, and readable by others. Small, hesitant course adjustments made late create confusion rather than clarity. A bold course alteration to starboard or a clear speed change is easier for others to interpret than small, frequent tweaks.
Whether approaching a harbor entrance or transiting a busy strait, the question to ask is always: "Would someone watching my AIS trace or observing my maneuver from the bridge of another vessel instantly understand what I am doing?".
SOLAS: when safety becomes international law
The Convention that the Titanic built
The SOLAS Convention in its successive forms is generally regarded as the most important of all international treaties concerning the safety of merchant ships. The first version was adopted in 1914, in response to the Titanic disaster, the second in 1929, the third in 1948, and the fourth in 1960.
Each iteration reflected the lessons of its era. The 1914 version mandated lifeboats for all on board, continuous radio watches, and ice patrol coordination - the direct failures that cost lives on the Titanic. The 1948 version absorbed the lessons of wartime seamanship. The 1960 version, the first adopted under the newly formed IMO, tackled fire safety and the growing size and speed of postwar shipping.
In 1974, a completely new Convention was adopted to allow SOLAS to be amended within a reasonable timescale, instead of the previous procedure which proved to be very slow. The key innovation was the tacit acceptance procedure: all amendments would enter into force on a specific date, unless there was an overt objection from a certain number of countries.
This replaced the old system under which every signatory had to ratify each change individually - a process that had become impossibly slow as the number of independent maritime nations grew. SOLAS 1974 came into force in 1980 and has been continuously updated since, now counting 167 contracting states representing approximately 99% of the world's merchant shipping tonnage.
What SOLAS covers - and what it means in practice
SOLAS is organized into chapters covering construction, fire protection, lifesaving appliances, radio communications, navigation, cargo handling, and more. It is a living set of rules that governments adopt, then enforce through their flag administrations and recognized organizations such as classification societies.
Think of each chapter as addressing a specific category of risk. Chapter II covers fire - one of the most feared hazards at sea - setting requirements for fire-resistant bulkheads, detection systems, and suppression equipment. Chapter III governs lifesaving appliances: how many liferafts a vessel must carry, how they are launched, how often drills must be held, and how equipment is maintained.
Chapter IV addresses radio and distress communications, incorporating the Global Maritime Distress and Safety System (GMDSS), which requires vessels to carry equipment - including EPIRBs (Emergency Position Indicating Radio Beacons) and SARTs (Search and Rescue Transponders) - that enables a distress signal to be sent and located from anywhere in the world. GMDSS has replaced Morse code as the standard, and the Automatic Identification System (AIS) is now mandatory for navigation purposes on qualifying vessels.
Applicability varies by vessel type and size. Commercial vessels above certain gross tonnage thresholds are fully inside SOLAS and must hold Safety Construction, Safety Equipment, and Safety Radio Certificates issued by their flag state. Private recreational yachts often fall outside the full scope, though many flag states require specific chapters or their equivalents by national regulation. But there is one chapter that cuts across all of these distinctions and reaches every vessel at sea - Chapter V.
Chapter V: the chapter that applies to every sailor
Chapter V covers Safety of Navigation, and unlike the rest of SOLAS, it does not stop at the commercial fleet. It applies broadly to all ships on all voyages - which in practice means that its core obligations touch recreational sailors too.
What does this mean in everyday terms? First, voyage planning. Chapter V formally requires that every voyage be properly planned before departure, taking into account all known hazards, weather forecasts, tidal conditions, and the limitations of the vessel and crew. For a recreational skipper, this is not a bureaucratic exercise - it is the habit of checking the forecast, identifying your waypoints, knowing your anchorage options, and briefing your crew before you leave the dock.
Second, the obligation to assist. Chapter V requires every master to render assistance to anyone found at sea in danger of being lost, when it can be done without serious danger to their own ship and crew. This is not optional, and it is not only a matter of seamanship tradition - it is a binding legal obligation under international law.
Third, distress signals and communication. Chapter V controls how distress messages are sent and interpreted, and requires vessels to respond appropriately when they receive one. Knowing how to use your VHF radio on Channel 16, how to activate an EPIRB, and how to interpret a MAYDAY call is not just good practice - under Chapter V, for vessels that carry this equipment, it is mandatory.
Finally, Chapter V governs the carriage of nautical charts and publications. A vessel must carry adequate, up-to-date charts for the waters it intends to navigate. For most recreational sailors today, this increasingly means electronic chart systems - provided they meet the applicable standards and are kept current.
Where COLREGs and SOLAS Meet
COLREGs and SOLAS are separate instruments with different scopes, but they are deeply complementary. COLREGs is the traffic law of the sea - it governs how vessels navigate in relation to one another. SOLAS governs the vessel itself - its construction, equipment, and operational readiness. Together they address the two fundamental questions of maritime safety: Will you avoid the collision? And: If something goes wrong, will you and your crew survive?
The connection is clearest around Chapter V. SOLAS requires passage planning; COLREGs defines how you navigate once underway. SOLAS mandates distress equipment so a call for help can be sent; COLREGs - and the long tradition of seamanship it codifies - ensures that other vessels respond. SOLAS insists you carry charts; COLREGs tells you how to read the buoyage marked on them.
Modern navigation tools bring these two pillars together in practical, accessible ways. A marine navigation app like Aqua Map displays up-to-date nautical charts that show buoyage, traffic separation schemes, and shipping lanes - the physical infrastructure that both regulations describe and require mariners to know.
Live AIS tracking allows any skipper to monitor surrounding vessel traffic in real time and assess risk of collision, turning Rule 7 from an abstract obligation into a continuous, informed practice. Integrated weather forecasts and passage planning tools support the Chapter V requirement to assess all relevant hazards before departure - and when conditions change at sea, real-time data allows plans to be adapted with the kind of situational awareness both regulations demand.
Technology does not replace the rules. It makes following them more intuitive, more reliable, and more consistent - which is precisely what good seamanship has always required.
From international law to everyday seamanship
COLREGs and SOLAS can feel remote when encountered as legal text - numbered rules, international conventions, chapters, annexes. But strip away the formal language, and both instruments are expressions of a very simple idea: the sea is shared, and sharing it safely requires everyone to follow the same framework of obligations and expectations.
COLREGs tell you how to behave toward other vessels: maintain a proper lookout, proceed at a safe speed, give way when required, and make your intentions unmistakably clear. SOLAS tells you how to prepare your vessel and yourself: plan your voyage, carry the right equipment, know how to use it, and be ready to help others in need.
Neither regulation asks the impossible. They ask for awareness, preparation, and sound judgment - qualities that any competent mariner already strives for. Knowing the law doesn't only keep you on the right side of it. It gives structure and confidence to decisions you may have to make in seconds, in the dark, in fog, with other vessels closing fast.
The sea has its rules. Now you know them.
