Charles River Aquatics
100 X 100s Masters Marathon Swim 2023


Boston Sports Institute 
900 Worcester Street
Wellesley, MA 

A portion of the proceeds from this event will be donated to the

Massachusetts General Hospital Pediatric Cancer Center

Sponsored by  


This is a fun, team-building event with swimmers and triathletes from around New England and the nation.

~All participants should be able to swim a 2:10 base interval or faster to finish 100x100 by the mandatory cutoff time. SUBMIT YOUR INTERVAL TIME WITH THIS LINK
~Space is limited. 
~Online Registration only. NO RACE DAY REGISTRATION
~This event is open to the public- please invite your swimmer and triathlete friends
~Participants must be 18 years old to participate
~There are no refunds if you cannot attend

Monday, April 18

  • 8:00 AM: Doors open
  • 8:00-8:45 AM: Warm-up and lane organization.  Use the Restrooms before you start.
  • 8:45 AM: All swimmers must be at their lane or in the water at their lane.
  • 8:50 AM: Mandatory Pre-Race Briefing & singing of the National Anthem, performed by CRA Head Coach Scott Mc Inerney.  All lanes should be organized at this time.  
  • 9:00 All lanes begin 100x100: We will have the new scoreboard to count the 100s for each interval. We will use the digital wall-clocks to follow intervals and track total time.
  • 1:00 PM: All swimmers must be out of the pool.


TIPS FOR THE 100x100:

  • BE AT YOUR LANE BY 8:45 AM (so we can organize lanes)
  • RESTROOM BREAKS:  Use the restrooms before you start as there will be no scheduled breaks during the 100x100. If you would like to make up the 100's you missed during restroom breaks there will be time for that at the end, however, all swimmers must exit the pool by 1:00 PM. 
  • SWIMMER'S BELONGINGS: Please do not bring valuables. There are no lockers, swimmers are to keep items on deck.
  • COVID/MASKING PROTOCOL: Masks are optional but encouraged for those who would like to wear them -- encourage social distancing as you see fit.
  • BRING EXTRA GOGGLES in case yours break.  We will provide free swim caps for participants.
  • EQUIPMENT: FINS are encouraged for those who are prone to shoulder injuries.  NO PADDLES: paddles are not allowed at this event because we have had issues with swimmers getting injured when hit by paddles.
  • HYDRATE CONTINUOUSLY. Please bring SPORTS DRINKS, WATER, GELS, GUs, AND SNACKS. Bring plastic bottles - NO GLASS ON DECK - that have easy-to-use squeeze tops, as you may not have time to unscrew conventional tops in between 100's. Mark your bottles with a recognizable feature, as many swimmers will be drinking the same brand and flavor of sports drink in the same lane. 
  • EAT BREAKFAST: Before you arrive, even if it is a small breakfast. Eat before the event and eat a meal soon after the event.  Fueling before, during and after will maximize your performance and your ability to recover. Bring easy-to-consume snacks such as Gels and GUs.  Do not bring messy items to eat during the event such as crackers, muffins, fruit, or any food item that will crumble and dirty the pool area. Each athlete is different in his/her caloric needs.  Assuming you start with a full fuel tank, plan on consuming 150-300 calories per hour during the swim; this is merely a general guideline.  Fuel early and fuel often during the event; DO NOT wait until you feel tired or hungry or thirsty.    
  • LANE ETIQUETTE: Please make sure everyone in your lane has space to finish on the wall (slide over when you touch the wall).  Be courteous to other swimmers, the coaches, and the lifeguards; disrespectful behavior will not be tolerated.  Listen to the CRM coaches on deck; they have the final say when making decisions.  Thank you.
  • ROTATE THE LANE LEADER: Swimmers are encouraged to rotate the lane leader every ten 100's, however, your lane must stay on the original send-off time in order to stay on the correct count. 
  • LANE ORGANIZATION BY INTERVAL: Details coming soon
  • INTERVAL TIMES:  Below are base intervals with the corresponding total time needed to complete 100x100, listed in Hours, Minutes, and Seconds. Most swimmers choose an interval of about 10 seconds slower than their normal base interval for training.


A good place to start is 10-15 seconds slower than your base interval, however, it also depends on your endurance and fitness level. Some swimmers can complete the 100x100 close to their base interval, while others will need to take it much slower in order to finish. Error on the conservative side (choose a larger interval) so you will have a better chance of finishing.


Interval                     Total Time

2:10                         3:36:40

2:05                         3:28:20

2:00                         3:20:00

1:55                         3:11:40

1:50                         3:03:20

1:45                         2:55:00

1:40                         2:46:40

1:35                         2:38:20

1:30                         2:30:00

1:25                         2:21:40

1:20                         2:13:20

1:15                         2:05:00

1:10                         1:56:40

1:05                         1:48:20

1:00                         1:40:00    



No matter how slow you go, you are still lapping everybody on the couch.