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Trial Swim

Overview of the trial swim

  •  One third of the distance of the big swim, maximum 16 km.

  •  In the same or similar body of water as the big swim.

  •  Attended by coach and Swim Master.

  • Pre-Trial-swim training log must be approved before the trial swim.

  • "Pass" is defined as finishing the trial swim without undue fatigue. Niagara to Toronto has a time limit due to the Humber current.

Before SSO will sanction a proposed swim, the swimmer must complete an outdoor, open water, continuous swim of one-third of the intended distance, or a maximum of sixteen kilometres (ten miles), to test the swimmer's readiness for a marathon swim. This swim cannot be in a swimming pool. It should be conducted in the same, or a similar, body of water, to that which is being challenged.  The Swim Master monitors this Trial Swim and ensures the necessary safety with respect to weather and accompanying boats and crew. The swimmer’s Coach should be in attendance throughout the Trial Swim.


Pre-Trial-Swim Preparation. During the training season, in order to prepare for the Trial Swim for a Lake Ontario swim, SSO recommends that the swimmer complete the following training swims:

  • A long continuous swim that is more than half the distance of the proposed swim, which may be done in a pool, and

  • Five open-water swims in a similar body of water to the lake being attempted.  Each swim should be of about 2 hours duration and include a variety of weather conditions including waves, cold water and night-time.

The swimmer MUST submit written-and-verified details of adequate preparation and have them approved by the Swim Master PRIOR to the date of the Trial Swim. It is recommended that the coach or trainer document these specific swims in the Pre-Trial-Swim Training Log (see Forms).


Once the Pre-trial-swim training log is approved, a Swim Master will conduct the Trial Swim. A location is chosen where the swimmer swims either parallel to the shore while the Swim Master and Coach observe on shore, or across a body of water, using boats and safety equipment.  The length of the course used for the Trial Swim must be measured by GPS.


A successful Trial Swim is judged by the completion of the prescribed distance without undue fatigue. The Swim Master may compare the speed in the second half to the first half of the Trial swim to assess fatigue and endurance. The Swim Master will also assess the adequacy of the feeding plan.

The Swim Master submits a report the Board of Directors of SSO on the acceptability of the Trial Swim. Judgement of the acceptability of the Trial Swim is the responsibility of the SSO Board.


Lake Ontario cut off time:

A comprehensive data-analysis (see Administration) of trial-swim times and Lake Ontario swim-outcomes (on the Niagara – Toronto route) since 1983 has demonstrated that:

  • Swimmers require sufficient endurance and speed to be successful in crossing the Humber River’s outflow and other circulation currents in the second half of their swim.  

  • Without sufficient endurance and speed, these currents add significantly to the length of the swim, leading to a level of exhaustion that has caused serious and potentially life-threatening medical complications which have warranted 2- to 3-day hospital admissions.

  • The 16 kilometre trial swim has proven to be a valid measure of a swimmer’s endurance and speed.

  • Trial swims over 6 hours and 45 minutes all resulted in Lake Ontario swims over 24 hours and resulted in serious medical complications requiring admission in 75% of cases.

  • Trial swims between 6:15 and 6:45 generally resulted in swims over 24 hours or inability to finish and extended emergency room visits in 2/3 cases.

Consequently, the following guidelines are established for the 16 km Trial Swim for a proposed Niagara-Toronto crossing:

  • < 6 hours 15 minutes: The Trial Swim is considered a PASS, if it is completed “without undue fatigue”.

  • 6:15-6:45: If the Board passes a trial swim in this zone, the Lake Ontario swim will be considered a "Specialized Support Swim" and the swimmer will be required to provide additional medical support, a second Swim Master, as well as other possible safety measures as determined by the Board.

  • >6:45: The trial swim is considered, without exception, a FAILED trail swim.

A swimmer must complete the Trial Swim in order to have SSO sanction the swim listed on the swimmer’s Registration Form.


A swimmer who does not complete the Trial Swim successfully can reapply for another Trial Swim.


During the Trial Swim, the swimmer should try to imitate as much as possible the conditions that will be experienced on the actual swim. Trying different types of food and practicing feeding is highly recommended (See Advice).  Immediately after the swim, a core temperature (rectal) reading can be taken to provide information about resistance to cold. 


If Pacers are to be used on the main swim, then it is important for the swimmer and pacers to practice swimming together; however, PACERS are NOT ALLOWED during the Trial swim.


Although night swimming is a valuable experience for the swimmer, this is not recommended for the Trial Swim, except under exceptional circumstances, and unless it is conducted by and with the consent of the actual Swim Master, who shall require all necessary safety procedures to be followed.


For swimmers who are resident outside of Ontario, SSO will accept evidence of a swim meeting the requirements of a trial swim, authenticated and signed by at least two witnesses, as a proxy for the Trial Swim. For verification purposes, such statement should include the signatories’ contact information. The report should include a description of the course, GPS points for the start and finish and any turn around points, a description of the weather including air and water temperature, wind and waves. We recommend the report follow the MSF guidelines.

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