The Global Rules of Marathon Swimming

The Marathon Swimmers Federation (MSF) Rules of Marathon Swimming are a set of standards and guidelines for undertaking a solo, unassisted open-water marathon swim in any body of water.

Disclaimer: Loneswimmer is one of the original authors.

These rules may be used by any swimmer who wishes to attempt a swim for which there is no local governing body. They also may be used by local governing bodies wishing to adopt a global standard, or as a foundation upon which to establish local exceptions.

The Spirit of Marathon Swimming

MSF Rules are guided by the traditions and spirit of unassisted marathon swimming.

Marathon swimmers embrace the challenge of crossing wild, open bodies of water with minimal assistance beyond their own physical strength and mental fortitude. There are ways to make the sport easier, but marathon swimmers consciously eschew them.

Marathon swimmers take pride that their achievements can be meaningfully compared to the achievements of previous generations, because the standard equipment of the sport has not changed significantly since 1875.

MSF Rules do not override local rules; they aim to codify their shared spirit.

“Golden Rules” of Marathon Swimming

  • Transparency of Swim Conduct –
    The intended conduct of the swim – including Swim Rules and any nonstandard equipment to be used – must be communicated fully and clearly before the swim begins, to everyone involved in the swim attempt, and in all public promotion. The declared rules and equipment may not be changed once the swim has begun.
  • Independent Observation –
    Independent and knowledgeable observers must document the facts of the swim and verify the swimmer’s adherence to the Swim Rules.

Swim Rules

This section defines standard MSF Swim Rules for a one-way solo swim (Point A to Point B). Standard rules for multi-leg swims, circumnavigation swims, relay swims, and stage swims are defined in the Special Swim Types supplement.

Individual swimmers or local governing bodies may adopt MSF Swim Rules in full, as shorthand for “standard conduct.” Or, they may adapt the rules to local circumstances, as long as two conditions are met:

1. Any modifications of standard swim conduct are declared.
2. The modifications do not violate the spirit of unassisted marathon swimming.

The declared Swim Rules must be read aloud by the observer in the presence of the swimmer and all support personnel before the swim begins.

Start & Finish
The swim begins when the swimmer enters the water from a natural shore. If geographic obstacles (e.g., cliffs) prevent the swimmer from clearing the water at the start, the swimmer may begin the swim by touching and releasing from part of the natural shore (e.g., cliff face).

The swim finishes when the swimmer clears the water on a natural shore, beyond which there is no navigable water. If geographic obstacles prevent the swimmer from clearing the water at the finish, the swimmer may finish by touching part of the natural shore.

Physical Contact
The swimmer may not make intentional supportive contact with any vessel, object, or support personnel at any time during the swim.


Standard Equipment
The swimmer may wear a single textile swimsuit with standard coverage, one latex or silicone cap, goggles, ear plugs, nose clips, and may grease the body. The swimmer may not use any additional equipment that benefits speed, buoyancy, endurance, or heat retention.


The swimmer may not intentionally draft behind any escort vessel or support swimmer. The swimmer may swim alongside an escort vessel, but may not intentionally position him or herself inside the vessel’s bow and displacement waves, except while feeding.

Support Swimmers
A support swimmer (or swimmers) may accompany the solo swimmer for a limited duration. Multiple support swims are allowed, but should not occur consecutively. The MSF recommends a maximum of one hour per support swim and a minimum of one hour between support swims.

The support swimmer may not intentionally touch the solo swimmer and must position him or herself at least slightly behind the solo swimmer.

Authority on the Escort Vessel
The observer is responsible for documenting the facts of the swim, interpreting the swim rules, and keeping the official time.

The pilot of the escort vessel (or lead pilot, if there are multiple vessels) is the ultimate authority in all other matters. The pilot may cancel the swim at any time, for any reason, including, but not limited to, concerns for the safety of the swimmer or support personnel. The pilot is responsible for following all relevant local maritime regulations.

Responsible Environmental Stewardship
Everyone involved in the swim attempt – swimmer, observer, support personnel, and escort boat personnel – must treat the environment respectfully and prevent avoidable harm to marine wildlife and ecosystems.

Continuance of the Spirit of Marathon Swimming
If any issue regarding swim conduct arises that the Swim Rules do not clearly address, the swimmer should act – and the observer should judge – in accordance with the spirit of unassisted marathon swimming.


The swim observer documents the facts of a swim and verifies the swim’s adherence to the declared rules. Documentation produced by a qualified observer is the single most important source material for authenticating a swim claim.

The primary qualifications of an observer are:

The observer must be capable of dispassionately evaluating the swim and its adherence to the declared rules. If the observer is acquainted with the swimmer, (s)he must be able to separate the personal relationship from his or her duties to observe, document, and verify.

The observer must be knowledgeable about the rules, traditions, and spirit of marathon swimming, and with the responsibilities of observing a marathon swim.

Local observer networks and official trainings are offered by following organizations:

  • Channel Swimming & Piloting Federation
  • Channel Swimming Association
  • Catalina Channel Swimming Federation
  • Santa Barbara Channel Swimming Association
  • NYC Swim
  • Observers who have not attended an official training may also demonstrate expertise through their personal history in the sport – as a swimmer, crew-member, or administrator.

Special Considerations

Very Long Swims

If a single observer is not able to maintain alertness for the entire duration of the swim, an additional observer is necessary. The MSF recommends two observers for swims anticipated to last longer than 18 hours, and three observers for swims anticipated to last longer than 30 hours. Overnight swims in the 10-18 hour range may also require a second observer.

On swims with multiple observers, a lead observer should be designated to coordinate the observer team and documentation procedures.

High-Profile or Unprecedented Swims

Swims of unusual magnitude or notoriety – especially unprecedented swims – demand a stricter standard for observer qualifications and reputation. In such cases, it is essential that the observers are trusted by the broader community of marathon swimmers.

A minimum of two highly qualified, reputable observers are recommended for high-profile swims, to reinforce their credibility.


Marathon Swim
A nonstop open-water swim, undertaken according to standardized rules, and requiring at least several hours of sustained effort to complete. Ten kilometers without significant assistance from currents is the minimum distance considered to be a marathon swim.

Remaining in the water for the entire duration of the swim from start to finish without intentional physical contact with escort vessels, support personnel, or other objects (fixed or floating).

Without artificial assistance to performance, other than the standard equipment of the sport. Any swim that benefits from assistance – in the form of nonstandard performance-enhancing equipment, supportive contact with the swimmer, or other violation of the spirit of unassisted marathon swimming – is considered an Assisted Swim.

Standard Equipment of Marathon Swimming

  • One swimsuit made of porous, textile material. For males, the suit must not extend below the knee or above the waist. For females it must not extend below the knee, onto the neck, or beyond the shoulder.
  • One bathing cap made of latex or silicone.
  • Goggles, earplugs, and noseclips.
  • Sunscreen and grease.
  • Safety lights for night visibility.
  • Simple timekeeping device (chronometer).
  • Escort boat, pilot, and crew.
  • Nutrition, and equipment to transport it between the boat and swimmer. The swimmer may not be supported or towed by the feed equipment.
  • Paddler(s) and support swimmer(s).
  • Observer(s).

The swimmer does not need to declare the use of standard equipment (i.e., it is assumed).

Any equipment not specifically listed here is considered nonstandard equipment.

Varieties of Nonstandard Equipment

Nonstandard equipment is anything not specifically included in the list of standard equipment. While it is impossible to exhaustively list all potential nonstandard equipment, we can categorize them as either;

1. Performance-enhancing, or
2. Non-performance enhancing.

Regardless of the performance benefit, swimmers must always declare use of nonstandard equipment in their swim rules and documentation.

Performance-Enhancing Equipment

Performance-enhancing equipment is defined as nonstandard equipment that benefits the swimmer’s speed, buoyancy, heat retention, or endurance. Swims using such equipment cannot be considered unassisted. Examples of performance-enhancing equipment include:

  • Equipment that may retain or increase warmth – e.g., wetsuits, neoprene caps, booties, gloves.
  • Equipment that may increase speed – e.g., flippers, paddles, shark cages.
  • Equipment that may increase buoyancy – e.g., pull buoys, wetsuits.
  • Auditory pacing aids – e.g., music players, metronomes.
  • Wearable electronic devices that transmit information to the swimmer beyond the time of day and elapsed time.
  • Underwater streamers.
  • Performance-enhancing drugs on the World Anti-Doping Agency List of Prohibited Substances.

Non-Performance-Enhancing Equipment

Non-performance-enhancing equipment provides no obvious benefit to performance, but nonetheless is not considered part of the standard equipment of marathon swimming. Swims using such equipment may still qualify as unassisted, but the equipment must be specifically declared in the swim rules and documentation.

Examples of non-performance-enhancing equipment include:

  • Swimwear with increased coverage – e.g., stinger suits, rash guards.
  • Wildlife deterrents – e.g., shark shields, shark divers, jellyfish sweepers. Note: harming marine wildlife violates the spirit of marathon swimming.
  • Wearable electronic devices that log data but do not transmit it to the swimmer.